The chemistry of penicillanic acids. Part III. A route to 1,2-secopenicillins

摘要

562 J.C.S. Perkin IThe Chemistry of Penicillanic Acids. Part 111.l A Route to 1.2-Seco-PenicillinsBy Edward G. Brain, Ian McMillan, John H. C. Nayler,' Robert Southgate, and Patricia Tolliday,Treatment of 6~-(triphenylmethylamino)penicillanates with certain alkylating agents in the presence of stronganhydrous bases causes S-alkylation and cleavage of the thiazolidine ring between the sulphur atom and C-2.The scope and possible mechanism of the reaction are discussed. A typical product, (3R,4R)-1 -(I -p-methoxy-benzyloxycarbonyl-2-methylprop-1 -enyl)-4-methylthio-3-(triphenylmethylamino)azetidin-2-one, has been con-verted into analogues of penicillins and cephalosporins containing a non-fused @-lactam ring.(7). We have now extended these model investigationsto a penicillin ester and related penicillanates containinga substituted 6p-arnino-gro~p.~Beecham Research Laboratories, Brockham Park, Betchworth, Surrey RH3 7AJWE reported in Part I1 that treatment of methyl penicil-lanate (1) or its 6a-bromo-derivative (2) with methyliodide and strong anhydrous base cleaved both the11) R'=R2=H( 2 ) R ' = H,R2= BrI 3 ' ) R' = R 2 = BrSMe8r HBrd02MeCO,.CH, P h( 4 ) R = H( 5 ) R = Br( 6 ) R = PhO-CHiC0.Nl-i( 8 1 R' = PhO- CHi CO ,R2= Me.I l l ) R' = Ph3C, R2= CH,*C,HL-OMe(p)( 9 ) R'= Ph,C,R*= W2Ph(10) R' = Ph,C, R2= C6tiL.No2(p(121 R' = Ph3C, R2= C0,Et(13) R' = PhCH(NH+CO, R*= HdO2R2thiazolidine and p-lactam rings to give compounds (4) and When phenoxymethylpenicillin methyl ester (8) was(5), respectively, whereas similar treatment of the 6,6- treated with methyl iodide and sodium hydride in tetra-dibromo-derivative (3) gave the non-fused azetidinone hydrofuran no @-lactam-containing transformationR.Southgate, J.C.S. Perkile I , 1974, 22.1 Part 11, J. P. Clayton, J. H. C. Nayler, M. J. Pearson, and s Preliminary report, J. P. Clayton, J. H. C. Nayler. R.Southgate, and P. Tolliday, Chem. Comm., 1971, 6901975 563products could be identified, but the ester (6) was isolatedin low yield. The stereochemistry of the methylthio-acrvloyl system was assigned by analogy with the evident/6Oi CH2Phm l e 320 / bsol; t ti transferH2Ndq+rsquo; -H Hbsol;H SMemfe 89 C0iCH2P hmle 264SCHEME Characteristic fragmentations in the mass spectrumof compound (19)tram-arrangement of the hydrogen atoms in the similarlyprepared ester (4) .l The compound is probably identicalwith one prepared by Kukolja and his co-workers by aroute which did not indicate the configuration.When benzyl 6p-triphenylmethylaminopenicillanate(9) was similarly treated with methyl iodide and sodiumhydride only the thiazolidine ring was cleaved, and theazetidinone (14) was isolated in reasonable yield.Thestereochemistry of this product was established byn.m.r. studies, which showed the characteristic cis-coupling of the p-lactam hydrogen atoms4 Detrityl-ation with toluene-@-sulphonic acid in acetone gave thecrystalline primary amine (19). The mass spectrum ofthis product showed the fragmentation pattern indicatedin the Scheme, and similar patterns proved to be highlycharacteristic of all the non-fused azetidinones reportedhere.The novel and selective cleavage of the 1,2-bond in 68-(triphenylmethy1amino)penicillanates appeared to be apromising starting point for the conversion of penicillinsinto related p-lactam-containing molecules.We there-fore studied the reaction in some detail, varying the estergroup, the base, and the alkylating agent.The methyl and 9-methoxybenzyl esters of GP-(tri-phenylmethy1amino)penicillanic acid behaved like thebenzyl ester in yielding 4-(methylthio)azetidin-2-ones ,but activated esters such as the 9-nitrophenyl ester (10)underwent preferential intramolecular rearrangement inwhich the methyl iodide took no part and could beomitted.The rearrangement product proved to be theanhydropenicillin analogue (25) , previously obtainedLetters, 1969, 3381.1966, 3326.9 S. Kukolja, R. D. G. Cooper, and R. B. Morin, TetrahedronK. D. Barrow and T. M. Spotswood, Tetrahedron Letters,5 S . Wolfe, Canad. J. Chem., 1968,46, 469.by the action of base on 6p-(triphenylmethylamino)-penicillanoyl chloride. In fact activated esters ofpenicillins generally give better yields of anhydropenicil-lins (26) than do the previously utilised acid chloridesor mixed anhydrides, either inorganic or organic basesbeing used for the conversion.Organic bases are also known to be useful in the intra-molecular S-alkylation whereby the chloro-ketones (27 ;X = phthalimido or acylamino) are converted into 3-oxocephams (28) .? Nevertheless organic bases, evensuch a strong one as 1,5-diazabicycl04.3.Onon-5-ene(DBN), proved unsuitable for converting 6p-(triphenyl-methy1amino)penicillanates into 4-( alkylt hio) azetidin-2-ones by intermolecular S-alkylation.In these reactions,however, sodium hydride could be successfully replacedby other strong inorganic bases such as potassium t-butoxide and also, surprisingly in view of the suscepti-bility of fused p-lactams to nucleophilic attack, bypowdered sodium hydroxide.Attempts to effect thiazolidine cleavage of the penicil-lanate (9) with other alkylating agents succeeded only( 2 5 ) R = Ph,C( 2 6 ) R = acyl(28)lsquo;CHRH H( 3 2 ) X = C0,Et( 3 3 ) X = Na( 3 4 )with certain of the more reactive halides.Thus no reac-tion occurred when methyl iodide was replaced by methyltoluene-@-sulphonate. Ethyl iodide and ethyl p-bromo-S. Wolfe, J. C. Godfrey. C. T. Holdrege, and Y. G. Perron,J. Amer. Chem. SOC., 1963, 85, 643; Canad. J . Chem., 1968, 46,2649.B. G. Ramsay and R. J. Stoodley, Chem. Comm., 1970,1617;J . Chem. SOC. ( C ) , 1971, 3859, 3864J.C.S. Perkinpropionate also failed to give 4-(alkylthio)azetidin-2-ones,possibly owing to olefin formation from the halides. Onthe other hand, esters of bromoacetic acid were usedsuccessfully and t-butyl bromoacetate gave particularlygood yields of the azetidinone (15). Satisfactory resultswere also obtained with allylic and benzylic halides,including allyl, p-methylallyl, cinnamyl, benzyl, P-methoxybenzyl, and @-nitrobenzyl bromides.Most ofthese reactions were conducted at room temperature, butreflux temperature was used with allyl bromide. Whenthe reaction with P-nitrobenzyl bromide was carried outat reflux, the normal product (16) was accompanied by aby-product formulated on spectroscopic evidence as (17),apparently resulting from further alkylation in the S-substituent .A different type of further alkylation was observedwhen the p-methoxybenzyl ester (11) was treated a troom temperature with methyl iodide and potassium t-butoxide, both present in excess. The normal product(20) was accompanied by another with spectroscopicproperties indicative of the py-unsaturated a-methylester structure (29).The dimethylated product (29) wasalso obtained when the monomethyl derivative (20) wasfurther treated with methyl iodide and strong base.The finding that base-promoted cleavage of the thiazo-lidine ring in structure (9) can be brought about onlywith certain alkyl halides suggests that the reactionprobably does not proceed by p-elimination followed byalkylation of an intermediate thiol (IS). It is equally un-likely that S-alkylation precedes p-elimination, sincesulphonium salts do not appear to be formed in theabsence of base. Another possible mechanism wouldinvolve attack on the sulphur atom by a carbene,generated by the action of base on the alkyl halide,followed by 1,2-bond cleavage in the sulphonium ylide(30).Indeed, subsequent to our work, it has beendemonstrated that carbenes generated by heating diazo-acetates with copper compounds attack penicillin estersin the absence of base to give 1,2-secopenicillin esters suchas (31), the double bond being shifted into conjugationwith the ester function on subsequent treatment withbase. However, if a carbene mechanism were operativein our process, reaction might be expected to proceedeven if the C-3 proton were not activated by a neighbour-ing ester group. We therefore treated the mixed an-hydride (12) with diethylamine to give the diethylamide,but found that no 1,2-bond cleavage occurred when thiswas treated with methyl iodide and sodium hydride intetrahydrofuran, even on prolonged refluxing.I t istherefore concluded that removal of the C-3 proton bybase is an integral part of our ring-cleavage reaction, andthat attack of the alkyl halide on sulphur then results inp-elimination as part of a concerted process.The finding that the 1,2-bond in 6p-(triphenylmethyl:amino)penicillanates can be cleaved without disturbingthe integrity of the 13-lactam ring or the stereochemistry8 M. Yoshimoto, S. Ishihara, E. Nakayama, E. Shoji, H.Kuwano, and N. Soma, Tetrahedron Lettevs, 1972, 4387; M.Numata, Y. Imashiro, I. Minamida, and M. Yamaoka, ibid., p.5097.of the substituents attached thereto has facilitated thepreparation of non-fused p-lactams which in otherstructural respects are direct analogues of the anti-bacterially active penicillins and cephalosporins.Thustreatment of compound (20) with toluene-@-sulphonicacid in acetone at 0" gave the toluene-P-sulphonate saltof the amine (21). The action of phenoxyacetyl chlorideon the free base then gave the ainide, and removal of the9-methoxybenzyl group with trifluoroacetic acid finallyafforded the penicillin V analogue (22).The amine (21) was also acylated with the mixed an-hydride (32), prepared from the condensation product(33) of sodium (R)-a-amino(pheny1)acetate and methylacetoacetate. Removal of the amine and carboxy-pro-tecting groups from (24) with trifluoroacetic acid gave theamorphous amino-acid (23), analogous to the importantantibiotics ampicillin (13) and cephalexin (34).Tests carried out by Mr. R. Sutherland and his col-leagues showed that neither 1,2-secopenicillin (22) or(23) had significant antibacterial activity.The anti-biotic effect of penicillins and cephalosporins is due toinhibition of membrane-bound enzymes involved in thelater stages of the completion of the bacterial cell wall.loAt least in some cases the inhibition appears to be ir-reversible, and has been attributed to acylation of theenzymes by the antibiotic, with opening of the P-lactamring. The inactivity of 1,2-secopenicillins could be dueto adoption of a conformation, different from that of themore rigid fused p-lactams, which is not accommodateda t the active site, or it could be a result of the muchreduced acylating power of non-fused p-lactams. Evi-dence of the latter is provided by the failure of 1,2-seco-penicillins to give hydroxamic acids when treated withneutral hydroxylamine under the conditions of a widely-used penicillin assay procedure.llEXPERIMENTALSodium hydride was used in the form of a 50 dispersionin oil.Tetrahydrofuran was distilled from CaH,. Othergeneral procedures were as described in Part 11.1Methylation of Phenoxymethylfienicillin Methyl Ester.-The ester (8) (2 g) in tetrahydrofuran (20 ml) was treatedwith methyl iodide (0.91 g) and sodium hydride (0.15 g) andstirred at room temperature for 3 h. The mixture was thendiluted with ethyl acetate (150 ml), washed with water, dried,and evaporated im vucuo. Chromatography of the residualgum (1.3 g) gave methyl 3-methyl-2-3-methylthio-2-(phenoxyacetamido)acrylamidocrotonate (6) (0- 14 g), m.p.158-160' (from ethyl acetate) (lit.,3 153"); A,,, 222(c 14,100) and 285 nm (15,440); vmx (Nujol) 3270, 1718,1678, 1638, and 1593 cm-l; 6 1.84 (3H, s ) , 2-14 (3H, s ) , 2.41(3H, s)., 3.71 (3H, s ) , 4.64 (2H, s), 6.85-7.50 (6H, m,aromatic and olefinic), 7.60br (lH, exch.), and 7.88br (lH,exch.); m/e 378 (M+) (Found: C, 57.1; H, 5-9; N, 7.3.Calc.for C,,H,,N,O,S: C, 57-1; H, 5.9; N, 7.4).Derivatives of 6 13-( Tp.ipheny1methylamino)fienicillanate.-(a) Benzyl ester. 6p-Aminopenicillanic acid (216 g) in9 G. R. Fosker, J. H. C. Nayler, and J. A. Wilcox, B.P.991,686/1966.lo J. L. Strominger, P. M. Blumberg, H. Suginaka, J. Umbreit,and G. G. Wickus, Proc. Ruy. Soc. ( B ) , 1971, 179, 369.l1 J.H. Ford, I d . and Eng. Chem. (Analytical), 1947,19, 10041975acetone (220 ml) was cooled (0") and treated with triethyl-amine (140 ml). After stirring for 30 min, and while main-taining the mixture at O', benzyl bromide (120 ml) inacetone (350 ml) was added in portions, and the mixture wasstirred at 0" for 4 h more, then poured into dry ether (3 1).The precipitate was filtered off and the filtrate washed withsodium hydrogen carbonate solution followed by water.The organic phase was treated with acetone (1 1) containingtoluene-p-sulphonic acid (190 g) to give a crystalline pre-cipitate of benzyl 6P-aminopenicillanate toluene-p-sulphon-ate salt (149 g), m.p. 155-158" (decomp.) (from methanol-ether) lit.,12 153-154' (decomp.) ; Y,, (Nujol) 1790 and1740 cni-l; 6 (CD,),SO 1.40 (3H, s), 1.63 (3H, s), 2.32(3H, s), 4.60 (lH, s), 5.15 (lH, d, J 4-5 Hz), 5.25 (ZH, s ) ,5.58 (lH, d, J 4.5 Hz), 7.15 (ZH, d, J 8 Hz), 7-42 (5H, s), 7.55(ZH, d, J 8 Hz), and 8-63br (3H, exch.). This salt (12 g) wasslurried with ethyl acetate and shaken with 5 sodiumhydrogen carbonate solution.The organic layer wasseparated, dried, and evaporated to give benzyl 6P-aniino-penicillanate (7.04 g) as an oil; vmax. 3500, 3400, 1780, and1750 cm-l; 6 1.42 (3H, s), 1.60 (3H, s ) , 1.85br (ZH, exch.),4.40 (lH, s), 4.53 (lH, d, J 4 Hz), 5.16 (ZH, s), 5.48 (lH, d,J 4 Hz), and 7-53 (5H, s). This ester (7 g) in dry methylenechloride (40 ml) was treated with triphenylmethyl chloride(7.7 g) and triethylamine (4.0 ml).After stirring for 1 h a troom temperature the solution was washed with water,dried, and evaporated. Crystallisation of the residue fromchloroform-ether gave benzyl GP-(triphenylmethylamino)-penicillanate (9.35 g), m.p. 210" (lit.,13 210") ; vmX. 1780 and1750 cm-l; 6 1.27 (3H, s), 1.53 (3H, s ) , 3.03br (lH, exch.),4-40 (lH, s), 4.47 (ZH, s, p-lactam protons), 5.08 (ZH, s ) , and7.1-7.65 (ZOH, m, aromatic).(b) p-Methoxybenzyl ester. In similar fashion 6P-amino-penicillanic acid (1 1.3 g) and p-methoxybenzyl bromide(10.26 g) furnished p-methoxybenzyl 6p-aminopenicillanatetoluene-p-szilphonate salt (6.7 g), m.p. 130-131" (fromacetone-ether) ; wmax, (Nujol) 1795 and 1760 cm-l; 6F(CD,),SO 1.37 (3H, s), 1-60 (3H, s), 2.30 (3H, s), 3.76 (3H,s), 4-52 (lH, s), 5.10 (lH, d, J 4.5 Hz), 5-15 (ZH, s), 5.53 (lH,d, J 4.5 Hz), and 6-8-7-7 (8H, m, aromatic) (Found: C,54.2; H, 6.6; N, 5-4; S,12-7.C2,H,,N,0,S, requires C,54.3; H, 5.6; N, 5.5; S, 12.6). This salt (38.1 g) wassuspended in dry methylene chloride (200 ml) and treatedwith triethylamine (1 7.3 g) , followed by triphenylmethylchloride (25.7 g) and more triethylamine (17 g). After 2 h atroom temperature the mixture was washed with wateI,dried, and evaporated to give a foam which was percolatedthrough silica, with chloroform as eluant. Crystallisationfrom ether gave p-methoxybenzyl 6P-(triphenylmethyl-amino)fieniciZlanate (11) (31.2 g), m.p. 137-139"; vmX. 1780and 1745 cm-l; 6 1.40 (3H, s), 1.51 (3H, s), 3.78 (lH, d, J 13Hz, exch.), 3.78 (3H, s), 4-37 (lH, s), 4.41-4-63 (ZH, m,collapsing to singlet on D,O exch., (3-lactam protons), 5.03(ZH, s), 6.85 (2H, d, J8Hz, aromatic), and 7.1-7.7 (17H, m,aromatic) (Found: C, 72.5; H, 6.0; N, 4.6; S, 5.6.C,,H,,N,O,S requires C, 72.7; H, 5.9; N, 4-4; S, 5.5).An ice-cold solution of 6p-(tri-phenylmethy1amino)penicillanic acid l3 (1.61 g) and triethyl-amine (0.36 g) in methylene chloride (30 ml) was treatedwith ethyl chloroformate (0.38 g).The mixture was allowedto attain room temperature during 1 h and the resultingmixed anhydride treated in situ with p-nitrophenol (0.49 g)in tetrahydrofuran ( 5 ml). Next morning the solution wasla A. M. Felix, J. Unowsky, J. Bontempo, and R. J. Fryer,J.Medicin. C h m . , 1968, 11, 929.(c) p-Nit'itrophenyl ester.washed with water and sodium hydrogen carbonate solution,dried, and evaporated. Crystallisation of the residualsyrup from ether gave p-nitrophenyl 6P-(tYiphenylmethyl-amino)penicillanate (10) (0.65 g), m.p. 176-178' (Found:C, 68.4; HI 5.4; N, 7.2. C,,H,,N,O,S requires C, 68.4;H, 5.0; N, 7.25).(d) Diethylamide. 6(3- (Triphenylmethy1amino)penicil-lanic acid (0.916 g) was converted into the mixed ethoxy-formic anhydride as in (c) and treated at 0" with diethyl-amine (0.146 g) in methylene chloride. The mixture wasallowed to attain room temperature during 1 h, worked upas in (c), and chromatographed to give NN-diethyl-6/3-(tri-phenylmethy1amino)penicillananaide (0-47 g) as an amorphouswhite solid; vmX.3500, 1772, and 1642 cm-l; 6 1.05 (3H, t,J 7 Hz) overlapping with 1.22 (3H, t, J 7 Hz), 1-33 (3H, s),1-57 (3H, s), 2.87-3.76 (5H, m, one exch.), 4.31 (lH, d, J 4Hz), 4.55 (lH, dd, J 4 and 6 Hz, collapsing to d, J 4 Hz, onD,O exch.), 4.64 (lH, s), and 7-0-7.67 (15H, m, aromatic)(Found: C, 72.1; HI 7.0; N, 7.8; S , 6.4. C,,H,,N,O,Srequires C, 72.5; H, 6.9; N, 8-2; S, 6.2).A lkylation of Benzyl 6p-( Tripheny1methylGcnzino)~enicil-Zanate.-(a) With methyl iodide. The ester (9) (10 g) intetrahydrofuran (300 ml) was treated with sodium hydride(0.5 g) and methyl iodide (28 g). After stirring for 15 h atroom temperature under nitrogen, the mixture was dilutedwith ethyl acetate (1 1) and washed with water. The driedorganic layer was evaporated to a solid (11.2 g) which wasseparated by chromatography into unchanged penicillanate(9) (5.25 g) and (3R,4R)- 1-( l-benzyloxycarbonyl-2-methyl-prop- l-enyl)-4-methylthio-3-( triphenylmethy1amino)azeti-din-2-one (14) (4-05 g), an amorphous solid, vmax 1760, 1720,and 1615 cm-l; 6 (CD,),CO 1-58 (3H, s), 1.93 (3H, s), 2.00(3H, s), 3.20 (lH, d, J 7 Hz, exch.), 4.42 (lH, dd, J 5 and 7Hz collapsing to d, J 5 Hz on D,O exch.), 4.56 (lH, d, J 5Hz), 4.96 and 5.25 (ZH, ABq, J 12.5 Hz), and 7.17-7.72(20H, m, aromatic).Detritylation of this product (1 equiv.of toluene-p-sulphonic acid in acetone at 0" overnight) andliberation of the free base gave (3R,4R)-3-amino-l-( l-benzyl-oxycarbonyl-2-methylp~op- 1-enyl) -4- (methylthio)azetidin-2-one(19), m.p.92-93", vnlax 3370, 1760, 1725, and 1630 cm-1,m/e 320 (M+) (Found: C, 59.9; HI 6-4; N, 8.7. Cl6H2,,N,- 0,s requires C, 59.9; HI 6.3; N, 8.7).The ester (9) (1.1 g) and t-butyl bromoacetate (0-43 g) in tetrahydrofuran (10 ml) andt-butyl alcohol (10 ml) was treated dropwise over 5 h with a0-9M-solution (2.44 ml) of potassium t-butoxide in t-butylalcohol, in tetrahydrofuran. After stirring at roomtemperature for 1 h more, the solution was concentrated tosmall volume, diluted with ethyl acetate, and washed withwater. The dried organic phase was evaporated and theresidual gum separated by chromatography into unchanged(9) (0.3 g) and amorphous (3R14R)-1-( l-benzyloxycarbonyl-2-methylprop- 1 -enyl) -4- (t-butoxycarbonylwzethylthio) -3- (tri-fihenylmethylamino)azetidin-2-one (15) (0.85 g), vmx 1760,1720br, and 1625 cn1-l; 6 1.40 (9H, s), 2.00 (3H, s), 2-22(3H, s), 2-33 and 2-68 (ZH, ABq, J 14 Hz), 2.96 (lH, d, J 8Hz, exch.), 4-50 (lH, dd, J 5 and 8 Hz, collapsing to d, J 5Hz on D,O exch.), 4-82 (lH, d, J 5 Hz), 4.98 and 5.22 (2H,ABq, J 12 Hz), and 7.1-7.6 (ZOH, m, aromatic) (Found:C, 72.1; H, 6.5; N, 3.9.C,,H,,N,O,S requires C, 72.5;HI 6.4; N, 4.2).(c) With allyl bromide. The ester (9) ( 5 g), allyl bromide(11.25 g), and sodium hydride (0.44 g) in tetrahydrofuranl3 J, C. Sheehan and K. R. Henery-Logan, J . Amev. Chew Soc.,1962, 84, 2983.(b) With t-butyl bromoacetate566 J.C.S. Perkin I(90 ml) were refluxed for 22 h under nitrogen. Usual work-up gave (3R,4R)-4-alZylthio- 1-( 1-benzyloxycarbonyl-2-methyl-prop- l-enyl)-3-(tri#henylmethylamino)azetidin-2-one (1 g) asneedles (from ether), m.p.110-111", vmX 1760, 1730,1625, 990, and 920 cm-l; 6 1.98 (3H, s), 2.20 (3H, s), 2.32(dd, J 14 and 8 Hz) and 2-64 (dd, J 14 and 6 Hz) (2H,SCH,), 2.96br (lH, exch.), 4.46-5.12 (6H, m, p-lactam,benzylic, and =CH, protons), 5.12-5.64 (IH, m), and 7.08-7-60 (20H, rn, aromatic) (Found: C, 75.2; H, 6.2; N, 4.7.C,,H,,N,O,S requires C, 75.6; H, 6-2; N, 4.8).A mixture of the ester(9) (23.6 g), p-methylallyl bromide (6.45 g, 1.1 mol. equiv.)and powdered sodium hydroxide (3.82 g, 2 mol. equiv.) intetrahydrofuran (500 ml) was stirred at room temperatureovernight, then evaporated in vacua. The residue waswashed with water and crystallised from ethyl acetate togive (3R,4R)-l-( l-benzyZoxycarbonyl-2-methyl~ro~-l-enyl)-4-(~-methylal~ythio)-3-(triphenylmethylamino) azetidin-Zone(18.6 g, 71y0), m.p.148-149O; v,, 3050, 2095, 1760, 1720,and 1635 cm-l; 6 1.6 (3H, s), 2.02 (3H, s), 2.23 (3H, s), 2.4and 2.76 (2H, ABq, J 14 Hz, SCH,), 306br (lH, exch.), 44-4.7 (4H, m, p-lactam protons and =CH,), 4.95 and 5-17 (2H,ABq, J 12 Hz, benzylic), and 7.1-7.7 (20H, m, aromatic)(Found: c, 76.0; H, 6-4; N, 4.7; s, 5.3. C,,H,,'N,O,Srequires C, 75.8; H, 6.3; N, 4.7; S, 5.3).(e) With cinnamyl bromide. The ester (9) (4.3 g) wasalkylated with cinnamyl bromide (1.71 g) by method (d) togive (3R,4R)- 1-( l-benzyZoxycarbonyl-8methyZ~r~- l-enyl)-4-(cinnamyZthio) -3- (triphenyZmethyZamino) azetidin-2-one (38 yo),m.p.139-140* (from ethyl acetate) ; vmx. 1735, 1718, and1630 cm-l; 6 1.96 (3H, s), 2.15 (3H, s), 2.3-3-1 (2H, m,SCH,), 2.8-3-lbr (lH, exch.), 4.56br (2H, s, fl-lactamprotons), 4.81 (2H, s, benzylic), 5.5-6-2 (2H, m, CHXH),and 74-7.7 (25H, m, aromatic) (Found: C, 78.1; H, 6-3;N, 4-2; S, 4.5. C,,H,,N,O,S requires C, 77.7; H, 6.0; N,4.2; S, 4.8).(f) With benzyl bromide. The ester (9) (6 g), sodiumhydride (0.49 g), and benzyl bromide (2.34 g) in tetrahydro-furan (1 10 ml) were stirred under nitrogen a t room tempera-ture for 48 h. Usual work-up gave unchanged (9) (0.6 g)and (3R, 4R) - 1 - ( 1 -benzyloxycarbonyl-2-methylprop- 1-enyl) -4-benzylthio-3- (triphenylmethylamino)azetidin-2-one ( 1.9 g)as an amorphous solid, vmX 1760, 1720, and 1625 cm-l;6 1.91 (3H, s), 2.15 (3H, s), 2-98 and 3-33 (2H, ABq, J 13.5Hz, SCH,), 2.96br (lH, exch.), 4.47br (2H, sharpening tosinglet on D20 exch.), 4.91 (2H, s), and 74-7.7 (25H, m,aromatic).Detritylation with 1 equiv. of toluene-p-sulphonic acid in acetone a t 0" for 4 h gave (3R,4R)-3-amino- 1-( l-benzyloxycarbonyZ-2-methylprop- l-enyl)-4-(benzyl-thio)azetidin-Zone toluene-p-sulphonate salt, m.p. 195-196"(from ethanol-ether); vwz (Nujol) 1795, 1725, and 1620cm-l; 6 (CD,),SO 1.88 (3H, s), 2.10 (3H, s), 2-28 (3H, s),3.82 (2H, s), 4.91 (lH, d, J 5 Hz), 5.08 (2H, s), 5.22 (lH, d, J6 Hz), 7.11 (2H, d, J 8 Hz), 7.25 (5H, s), 7.35 (SH, s), 7-57(2H, d, J 8 Hz), and 8.86-9-20br (3H) (Found: C, 61-2;H, 5.6; N, 4.8; S, 11-5.C,,H3,NzO8S, requires C, 61.3;H, 5.7; N, 4.9; S, 11-3y0).Reaction of the ester(9) (46 g) with p-methoxybenzyl bromide (19 g) by method(d) gave (3R,4R)- 1-( l-benzyZoxycarbonyl-2-uvtethyZ~ro~-l-enyl) -4- (p-methoxybenzylthio) - 3- (triphenylwaethylarnina) axeti-din-2-one as a foam (40 g) ; vmx. 1760, 1720, and 1630 cm-l;6 1.91 (3H, s), 2-15 (3H, s), 2.93 and 3.29 (2H, ABq, J 14 Hz,covering broad NH signal at 6 ca. 2.9), 3.27 (3H, s), 4.48br(2H, collapsing to singlet on D,O exch., @-lactam protons),(d) With p-methylallyl bromide.(g) With p-methoxybenzyl bromide.4.94 (2H, s), 6-71 (2H, d, J 9 Hz, aromatic), 6.95 (2H, d, J 9Hz, aromatic), and 701-7.8 (20H, m, aromatic) (Found:M+, 668.2675. C,,H,,N,O,S requires M , 668.2709).De-tritylation gave (3R,QR)-3-amino- 1-( l-benzyEoxycarbmyl-2-methylpro#- l-enyE)-4-(p-methoxybenzyZthio) azetidiut-2-onetolwene-p-sulphonate salt, m.p. 172-173O (from acetone) ;vm (Nujol) 1800, 1725, and 1630 cm-l; 6 (CD,),SO 1.92(3H, s), 2.10 (3H, s), 2.28 (3H, s), 3.70 (3H, s), 3.78 (2H, s),4.95 (lH, d, J 6 Hz), 6.12 (2H, s), 5.25 (lH, d, J 5 Hz), 697-7.7 (13H, m, aromatic), and 9.0br (3H, exch.) (Found: C,60.0; H, 5.6; N, 4.4; S, 11.3. C,,H,,N,O,S, requires C,60.2; H, 6.7; N, 4.7; S, 10.7).(h) With p-nitrobenzyl bromide. The ester (9) (2 g) intetrahydrofuran (60 ml) was stirred with sodium hydride(0.2 g) and P-nitrobenzyl bromide (0.79 g) at room tempera-ture for 48 h. Usual work-up gave unchanged (9) (0.82 g)and (3R,4R)- 1- (l-ben~yloxycarbonyl-2-methylpro~- l-enyl)-4-(p-nitrobenzylthio) -3-( triphenylmethylamino)azetidin-2-one(16) (0.6 g), m.p.148-150" (from ether); vmx 1760, 1720,1625, 1520, and 1340 cm-l; 6 1.93 (3H, s), 2.12 (3H, s) 2.97br(lH, exch.), 3.03 and 3.36 (2H, ABq, J 14 Hz), 4.48br (2H,s, changing to d, 6 4.47, J 5 Hz, and d, 6 4.56, J 5 Hz on D20exch.), 4.81 and 5-08 (2H, ABq, J 12 Hz), 74-7.6 (22H, m,aromatic), and 8-00 (2H, d, J 9 Hz, aromatic) (Found: C,72.1; H, 5-6; N, 6-1. C,,H,,NSO,S requires C, 72.0; H,5.5; N, 6.1).In another experiment the ester (9) (22 g), 9-nitrobenzylbromide (9 g), and sodium hydride (4 g) in tetrahydrofuran(600 ml) were refluxed for 8 h. Usual work-up gave un-changed (9) (log), the azetidinone (16) (1.85 g), and (3R,4R)-I-( 1-benzyloxycarbony2-2-methylprop- l-enyl)-4- lJ2-bis-(p-nitrophenyl)ethylthio-3- (triphenylmethylamino) azetidin-Zone(17) (0.6 g), m.p.210' (from ether); vmsx 1760, 1720, 1630,1525, and 1350 cm-1; 6 1-81 (3H, s), 2.0 (3H, s), 2.8-304(4H, m, one exch.), 4.35 (lH, d, J 5 Hz), 4.53 (lH, complex,sharpens to d, J 5 Hz, on D20 exch.), 4.82br (2H, s, benzylic),6.88-7.09 and 7-84-8.07 (two sets of 4H, $-subst. phenyls),and 7.2-7.8 (m, phenyls) (total aromatic integral ca. 28H)(Found: C, 70.4; H, 5.2; N, 6.9; S, 4.1. C4,H4,N,0,Srequires C, 70.4; H, 5.1; N, 6.9; S, 3.9).Attempted Methylation of p-Nitrophenyl 6p-( TrifihefiyZ-methyZamino)pewicilZunate.-The ester (10) (1 16 mg) intetrahydrofuran (5 ml) was stirred with sodium hydride (20mg) and methyl iodide (0.4 ml) for 2 h, rapidly becomingyellow. Usual work-up gave (5R, 6R)-3-isopropylidene-6-(triphenylmethylamino)-2-oxopenam (25) ; vmK 1785, 1700,and 1640 cm-l; 6 1.98 (3H.s), 2-10 (3H, s), 3.10 (lH, d, J 11Hz, exch.), 4.42 (lH, d, J 4 Hz), 4.87 (lH, dd, J 4 and I1 Hz,collapsing to d on D,O exch.), and 702-7.7 (15H, m) ; m.p.133" (lit.,6 134-135deg;). The same product was obtained inthe absence of alkylating agent, by using either sodiumhydride or 1,5-diazabicyclo4.3.0non-6-ene as the base.Methylation of p-MethoxybenxyZ Gp-(Triphenylrnethyl-amino)peniciZZanaie.- (a) One equivalent of 9otassium t-butoxide. The ester (11) (2 g) and methyl iodide (7 ml) intetrahydrofuran (40 ml) were stirred under nitrogen for 4 hwhile a 1M-solution (3.4 ml) of potassium t-butoxide in t-butyl alcahol, in tetrahydrofuran was added dropwise.Themixture was then stirred for a further 30 min, diluted withethyl acetate (200 ml), washed with water, dried, andevaporated in vacuo. Purification of the residue bychromatography, followed by crystallisation from ether,gave (3R,4R)- 1-( l-p-metlaoxybenzyEoxycarbonyl-2-methyZ~ro~1 -enyl) -4-medhylthio- 3- (triphenylmethylamino) azetidin- 2-0-(20) (0-5 g), m.p. 126-128"; v,, 1760, 1718, and 1615 cm-11975 5676 (CD,),CO 1.55 (3H, s ) , 1.93 (3H, s ) , 2.17 (3H s ) , 3-18 (lH,d, J 8 Hz, exch.), 3.77 (3H, s), 4.40 (lH, dd, J 5 and 8 Hz,collapsing to d, J 5 Hz, on D20 exch.), 4.53 (lH, d, J 5 Hz),4.87 and 5.18 (2H, ABq, J 12 Hz), 6.83 (2H, d, J 9 Hz,aromatic), and 7-1-7-7 (17H, m, aromatic) (Found: C,73.3; H, 6.2; N, 5.0; S, 5.3; M+, 592.2344.Ca6H3,-N,04S requires C, 73.0; H, 6.1; N, 4-7; S, 5.4; M ,592.2396). Further crude (20) (1-2 g) recovered from theethereal mother liquors was dissolved in the minimumvolume of acetone, cooled (- 20') , treated with toluene-$-sulphonic acid monohydrate (0.42 g) in acetone, and setaside overnight a t 0' to give crystals of (3R,4R)-3-umino-l-( 1-p-methoxyben.zyloxycarbonyl-2-methy~pro~- l-enyo-4- (methyE-thio)azetadin-2-one-p-toZuenesd~honate salt (0-7 g), m.p.154-155' (from acetone) ; v,, (Nujol) 1805,1722, and 1630cm-l; 6 (CD,),SO 1.95 (3H, s), 2.05 (3H, s), 2.18 (3H, s),2.30 (3H, s), 3.75 (3H, s), 4.88 (lH, d, J 5 Hz), 5.13 (lH, d,J 5 Hz) partially obscured by 5.18 (2H, s), 6-86-7.66 (8H,m, aromatic), and 8.75vbr (3H, exch.) (Found: C, 54.7; H,5.8; N, 5.2; S, 12-1.C24H,0N20,S2 requiresc, 55.2; H, 5.8;N, 6.4; S, 12.3). The free base (21) was obtained ascrystals (from ether) , m.p. 78-79'; v,, 1760, 1720, and1630 cm-l; 6 1-73br (2H, s, exch.), 2.00 (6H, s), 2.22 (3H, s),2.80 (3H, s), 4.38 (lH, d, J 6 Hz), 4.96 (lH, d, J 6 Hz), 4-98and 5.26 (2H, AEQ, J 12 Hz), 6.86 (2H, d, J 9 Hz, aromatic),and 7.30 (2H, d, J 9 Hz, aromatic) (Found: C, 58.5; H, 6.3;N, 7.8; S, 9.1. C,,H2,N204S requires C, 58.3; H, 6-3; N,The ester (11) (0.5 g)in tetrahydrofuran (20 ml) was stirred with methyl iodide(7 ml) for 4 h while a 1M-solution (2.0 ml, 2.3 equiv.) ofpotassium t-butoxide in t-butyl alcohol, in tetrahydrofuran,was added dropwise.The solution was set aside overnightand worked up as in (a). Chromatography gave (20) (0.2 g)and (3R, 4R)- 1-( l-p-methoxybenzyloxycarbonyZ- 1, Z-dimethyZ-prop- 2-enyZ)-4-methyZthio-3-(triphenyZmethylamino) azetidin-2-one (29) (0.25 g), apparently as a single isomer, m.p. 153-166' (from ethyl acetate-light petroleum); v- 1760 and1738 cm-l; 8 1-57 (3H, s), 1.75 (3H, s), 1.77 (3H, d, J 1 Hz),2.98 (lH, d, J 6 Hz, exch.), 3.75 (3H, s), 4-16 (lH, d, J 5 Hz),4.3 (IH, partially obscured, collapsing to d, J 6 Hz, 8 4-33on D20 exch.), 4-80 (LH, s), 5-00 (lH, d, J 1 Hz), 5.07 (2H,s), 6.80 (2H, d, J 9 Hz, aromatic), and 7-0-7.7 (17H, m,aromatic) (Found: C, 73.8; H, 6.5; N, 4.5; S, 5.5; M+,606.2552. C,,H,,W,O,S requires C, 73.2; H, 6.3; N, 4.6;S, 5.3 ; M , 606.2662).Use of a greater excessof potassiumt-butoxide (ca. 5 equiv.) gave (29) as the major product(3R, 4R) - 1 - ( 1-Carboxy-2-methylprop- 1-enyZ) -4-methyZthio-3-(~henoxyacetamido)azet~din-2-one (22) .-The amine (21) (1.25g) in methylene chloride (30 ml) was treated with tridhyl-amine (1.54 ml) and cooled to - 2 O O . A solution of phen-oxyacetyl chloride (0.62 g) in methylene chloride (10 ml) wasadded dropwise over a few minutes. After a further 6 rninat -10" the mixture was washed with water, dried, andevaporated. Crystallisation of the residue (0-91 g) fromethyl acetate gave (3R,4R)-1-( l-p-methoxybenzyloxycarbonyl-2-methylprop- 1 -enyE) -4-methylthio-3-(phenoxyacetamido) -azetidin-bone, m.p.120-122", vmL 3400, 1770, 1720, 1695,8.0; s, 9.2).(b) Potassium t-butoxide in excess.(75).and 1615 cm-1; 6 1.85 (3H, s), 2.00 (3H, s), 2.25 (3H, s), 3.79(3H, s), 4.56 (2H, s), 6.00and 5-28 (2H, ABq, J 12 Hz), 5.06(lH, d, J 5 Hz), 5.47 (lH, dd, J 5 and 9 Hz), and 6.8-7.6(lOH, m, aromatic and NH) (Found: C, 614; H, 5-9; N,5.7. C,H28N20,S requires C, 61-9; H, 5.8; N, 5.8).This ester (1.1 g) in dry benzene (10 ml) was cooled (ca. 5')and treated with trifluoroacetic acid (7 ml), then allowed toattain room temperature. After 90 min trifluoroacetic acidwas removed by co-distillation with benzene (3 evapor-ations). The residue was dissolved in chloroform and ex-tracted with sodium hydrogen carbonate solution ( 0 .2 ~ ; 80ml). The extracts were acidified with hydrochloric acid andthemselves extracted with ethyl acetate. Evaporation ofthe dried organic phase gave the acid (22) as an amorphoussolid (0.4 g), A,, 235 nm (e 5300); vmaL 3400, 2600br, 1770,1690br, and 1630 cm-1; 6 2.00 (3H, s), 2.05 (3H, s), 2.30 (3H,s), 4.63 (2H, s), 5.26 (lH, d, J 5 Hz), 5.56 (lH, dd, J 8 and 5Hz, collapsing to d, J 5 Hz, on D20 exch.), 6.8-7.6 (6H, m,one exch.), and 7.66 (lH, d, J 8.5 Hz, exch.).(3R, 4R) - 3- ( R) -a-A mim ( phenyl) acetamido - 1 - ( 1 -carbox)-2-methyZPr@- l-enyZ)-4-(methyZthio)azetidi.n-2-one (23) .-Sodium (R) -a*( 1-methoxycarbonylprop-2-eny1amino)phen-ylacetate (33) (1.04 g) in ethyl acetate (15 ml) was cooledto - 15' and treated with N-methylmorpholine (3 drops) andethyl chloroformate (0.39 ml). The mixture was stirred at-15' for 5 min to complete formation of the mixed an-hydride (32), then treated dropwise at the same temperaturewith the amine (21) (1.4 g) in ethyl acetate (15 ml) during10 min. The mixture was set aside at room temperature for30 min, then washed with sodium hydrogen carbonate solu-tion and water. The dried organic layer was evaporated andthe residue chromatographed to give amorphous (3R,4R)-1-(l-p-methoxybenzyloxyca~bonyl-2-methyl~ro~- l-enyl)-3-( H)-a-( l-nzethoxycarbonyl~~o~-2-enylamino) (PhenyZ) acetavnido J-4-(methyZthio)uzetidin-2-one (24) (0.79 g ) , vmx. 3390, 3250, 1770,1710-1690br, and 1656 cm-1; 6 1.55 (3H, s), 1.82 (3H, s),1.90 (3H), 2.22 (3H, s), 3.63 (3H, s), 3.78 (3H, s), 4-58 (lH, s),4-93 (lH, d, J 5 Hz), 5.00 and 5.25 (2H, ABq, J 12 Hz,covering doublet, lH, J 7 Hz at 6 5-15, collapsing to singleton D,O exch.), 5.45 (lH, dd, J 9 and 5 Hz collapsing to d,J 5 Hz on D20 exch.) , 6.8-7.6 (lOH, m, one exch., aromaticand NH), and 9.45 (lH, d, J 7 Hz, exch.) (Found: C, 62.0;H, 6.2; N, 7.1; S, 5.5. C,0H,,N307S requires C, 61.9; H,6.0; N, 7.2; S, 5.5). The protected ester (24) (0-2 g) inbenzene (1 ml) was cooled (ice-bath) and treated with tri-fluoroacetic acid (0.2 ml). The mixture was kept a t roomtemperature for 45 min, then trifluoroacetic acid was re-moved by co-distillation with benzene (3 evaporations).Trituration with ether gave the amorphous trifluoroacetatesalt of the amino-acid (23) (0.136 g), A,, 240 nm (e 4470);v- (Nujol) 1760 and 1680br cm'l; 8 (CD,),SO 1-07 (3H,Hz, partially obscured), 5-40 (lH, dd, J 8 and 4.5 Hz,collapsing to d, J 4.6 Hz on D20 exch.), 7-56 (5H, s, coveringbroad 1H exch.), and 9.56 (lH, d, J 8 Hz, exch.).s), 2-00 (3H, s ) , 2.22 (3H, s), 6.13 (lH, s), 5.16 (lH, d, J 4.6We thank Dr. R. J. Stoodley for discussions.4/1986 Received, 27th September, 1974