Branched-chain sugars. Part V. Identification and synthesis of vinelose

摘要

1292 J.C.S. Perkin IBranched-chain sugars. Part V.l Identification and Synthesis of Vinel-oseBy John S. Brimacombe, Safia Mahmood, and Anthony J. Rollins, Department of Chemistry, University of6-Deoxy-2-0.3-C-dimethyl-L-talose (24) has been synthesised from 1,2-O-isopropylidene-3-C-methyl-a-~-allofuranose (3) and shown to be identical with vinelose. a component of two cytidine nucleotides isolated fromAzotobacter vinelandii strain 0.Dundee, Dundee DD1 4HNTHE branched-chain sugar vinelose occurs 3*4 as a com-ponent of two cytidine nucleotides isolated from culturesof Azotobacter vinelandii strain 0, and these representthe first examples of a new class of sugar nucleotideisolated from living cells. Chemical and spectroscopicevidence indicated 5,6 that vinelose is a 6-deoxy-2-0,3-C-dimethyl-L-aldohexose possessing the allo-, altro-,galacto-, or talo-configuration ; however, the firststructure was eliminated when vinelose was shown tobe chromatographically and spectroscopically distin-guishable from synthetic 6-deoxy-2-0,3-C-dimethyl-~-allose.' Since vinelose has not been crystallised and nocrystalline derivatives of the free sugar are at presentavailable, thereby precluding determination of itsstructure by X-ray crystallographic analysis, we under-took a synthesis of 6-deoxy-2-0,3-C-dimethyl-~-talose(24), which seemed to be the most likely structure forvinelose from a consideration of the available data.5*6In Part I * it was shown that 1,2:5,6-di-O-isopropyl-idene-a-D-rzbo-hexof uranos-3-ulose ( 1) undergoes a highlyPart IV, J.S. Brimacombe, J. Minshall, and C. W. Smith,J.C.S. Perkin I , 1975, 682.Preliminary communication, J. S. Brimacombe, S. Mahmood,and A. J. Rollins, Carbohydrate Res., 1974,38, C7.S. Okuda, N. Suzuki, and S. Suzuki, Seikagaku, 1961, 33,667.S. Okuda, N. Suzuki, and S. Suzuki, Biochim. Biophys. Acta,1964, 82, 436.stereoselective reaction with methylmagnesium iodide toform 1,2:5,6-di-O-isopropylidene-3-C-met hyl-a-D-allo-furanose (2), which was subsequently transformed, viathe trio1 (3), into 6-deoxy-l,2-0-isopropylidene-3-C-methyl-a-D-allofuranose (4). It seemed that entry intothe L-talo-series would be achieved most readily by anucleophilic displacement reaction on the derived5-toluene-$-sulphonate (5).However, treatment of thissulphonate with benzoate ion in hot NN-dimethyl-formamide gave only ca. 5 yield of 5-0-benzoyl-6-deoxy-l,2-0-isopropylidene-3-C-methyl-~-~-talofuranose(6), and the presence of a number of other products,possibly arising from bimolecular elimination of thesulphonyloxy-group, was revealed by t .l.c. Othermeans of inverting the configuration a t C-5 of anappropriate D-allofuranose derivative were thereforesought.In the first method examined, 1,2-0-isopropylidene-3-C-methyl-5,6-di-O-~-tolylsulphonyl-a-~-allofuran0~e (7)was heated with benzoate ion in NN-dimethylformamideS. Okuda, N. Suzuki, and S. Suzuki, J . Biol. Chern., 1967,242, 958.6 S. Okuda, N. Suzuki, and S. Suzuki, J . Biol. Chem., 1968,243, 6353.G. B.Howarth, W. A. Szarek, and J. K. N. Jones, Canad. J .Chem., 1968, 46, 3376. * J. S. Brimacombe, A. J. Rollins, and S. W. Thompson,Carbohydrate Res., 1973, 81, 1081975 1293to afford a mixture of 5,6-di-0-benzoyl-l,2-O-iso-propylidene-3-C-methyl-~-~-talofuranose (10) and thecorresponding 6-benzoate (1 1). Further benzoylationof the monobenzoate (11) gave the dibenzoate (lo),thus establishing that they possess the same absoluteconfiguration. The L-talo-configuration of the benzoates(10) and (1 1) followed from the fact that they were readilydistinguishable (mixed m.p.s) from the epimeric benzo-ates (12) and (13), obtained by benzoylation of 1,2-0-isopropylidene-3-C-methyl-ot-~-allofuranose (3). Al-though the structure of the monobenzoate (1 l) was notrigorously established, esterification of the primaryhydroxy-group seems most probable by analogy witha similar displacement on 1,2-0-isopropylidene-3-0-methyl-5,6-di-O-methylsulphonyl-a-~-allofuranose (14)Lie.an unbranched isomer of (7). The latter andrelated lo studies have demonstrated that displacementswith benzoate and acetate ions in such solvents asNN-dimethylformamide are generally effected by S N 2processes. Thus, the dibenzoate (10) can be assumedto be formed principally by a direct displacement withbenzoate ion on 6-O-benzoyl-l,2-0-isopropylidene-3-C-methyl-5-0-~-tolylsulphonyl-ot-~-allofuranose ( 8 ) , formed,0--CH2 0-CH, 4 H Me2cO_CH0C H2.0 R'R20-l-HHO b, O-CMe2( 3 ) R ' = R ~ = H(71 R'=R~=TS(12) R'= R ~ = BZ(13) R'= BZ.R~ = HHO Q, O--CMe2Q, HO O-CMe2MeRO A Hbsol; HO O-CMe214) R = H(5) R = TsCH2* OMSM s O t Hby a similar displacement of the more reactive primarysulphonyloxy-group of the disulphonate (7).However,@ J. S. Brimacombe, A. M. Mofti, and L. C. N. Tucker, J .Chem. SOC. (C), 1971, 2911.the formation of the monobenzoate (1 1) indicates thatthe pathway involving the external nucleophile isf'h OH2 bsol;A*competitive with one involving intramolecular partici-pation by the 6-benzoyloxy-group. The latter pathwaywould produce more dibenzoate (10) and the mono-benzoate (11) by attack of benzoate ion and adventitiouswater, respectively, on the intermediate dioxolaniumion (9) in the manner indicated.Entry into the L-talo-series is achieved in acceptable yield by this pro-cedure, which could be adapted easily to a synthesis ofvinelose (see later) following de-esterification of thedi- and mono-benzoates (10) and (1 1).The method finally adopted in the synthesis proceededthrough the formation and reductive ring opening of5,6-anhydro-l,2-0-isopropylidene-3-C-met hyl- p-~-talo-furanose (17) (see Scheme). Thus, sulphonylation ofthe monobenzoate (13), prepared by unimolar benzoyl-ation of the trio1 (3) ,* furnished 6-O-benzoyl-l,2-0-isopropylidene-3-C-met hyl-5-0-fi-t olylsulphonyl-~-~-allofuranose (15). On brief treatment (ca. 2 h) of thelatter with methanolic sodium methoxide at -25 "C, theoxiran (17) was obtained in ca. 15 yield via the mono-sulphonate (16) formed initially. A substantial pro-portion of the oxiran (17) was further converted into1,2-0-isopropylidene-3-C,6-0-dimet hyl-P-~-talofuranose(18) by regiospecific opening at C-6 with methoxide ion;the methylated derivative (18) was the only productdetected and isolated when the reaction was allowed toproceed for ca.10 h. Unacceptable loss of the oxiran(17) by ring opening with methoxide ion was avoidedby isolation of the intermediate sulphonate (16) follow-ing brief treatment (ca. 1 h) of compound (15) withmethanolic sodium methoxide at -25 "C. Whereaslo R. C. Chalk, D. H. Ball, M. A. Lintner, and L. Long, jun.,Chem. Comm., 1970, 245; hT. MiljkoviC. A. JokiC, and E. A.Davidson, Caybohydrate Res., 1971, 17, 1551294 J.C.S.Perkin Ithe sulphonate (16) gave only a low yield of the oxiran acid. The i.r. (KBr disc) and mass spectra, optical(17) on treatment with methanolic sodium methoxide rotation, and paper chromatographic and electrophoretica t -25 "C, this transformation was accomplished in properties of the synthetic branched-chain sugar were87 yield on heating the sulphonate (16) in benzene indistinguishable from those of vinelose. Further, thewith the non-nucleophilic base 1,5-diazabicyclo5.4.0- n.m.r. spectra and physical properties of the alditolundec-5-ene (DBU). Regiospecific opening of the (25), prepared by reduction of the free sugar (24) withoxiran (17) with lithium aluminium hydride thentalofuranose (19), from which was prepared a benzoate(6) identical with that obtained from the benzoate-exchange reaction on the 6-deoxy-~-allofuranose sul-phonate (5).The 3- and 5-hydroxy-groups of the diol (19) werenext protected by benzylationll and the product (20),on refluxing with methanolic hydrogen chloride, yieldeda mixture of methyl 3,5-di-O-benzyl-6-deoxy-3-C-methyl-a- and -p-L-talofuranosides (21), from which the corre-sponding 2-O-methyl ethers (22) were obtained.llafforded 6-deoxy- 1,2-O-isopropylidene-3-C-met hyl- (3-L- CHZ*ORH :$ RO Me125) R t H(26) R = Acsodium borohydride, and the derived triacetate (26)also proved to be indistinguishable from those of thesame derivatives obtained from natural vinelose.The foregoing synthesis establishes vinelose to be6-deoxy-2-0,3-C-dimethyl-~-talose (24).The same con-( 3 ) i,ii, R 2 0 ~ o , z ~ ~ " w E H f $ * bsol; clusion appeared was in reached preliminary by Funabashi form just et prior aZ.,12 whose to our results own.2Ho o-cMe2 The Japanese workers used an essentially similarapproach and the two syntheses converge in theirCH~-OR' CHrOHHO O--CMe2 HO O-CMe2(13)R'=Bz, R2=H( 15)R'=Bt, R2= TSMeH+O.CHzPh BHaoMe PhCHit) OR( 21) R = H(22)R= Mel i x,?.OHD H , 0 M eHO 6Me(231EXPERIMENTAL CHrOMeT.1.c. was performed on Kieselgel G; spots were locatedwith vanillin-sulphuric acid.13 Unless otherwise indicated,2 i i , v * : - H G ~ i.r. spectra were recorded for Nujol mulls on a Perkin-Elmer Infracord spectrometer, and n.m.r. spectra weresolutions in deuteriochloroform with tetramethylsilane as(19) R = H (16) internal reference.Optical rotations were measured at(20) R = CH2Ph ambient temperature with a Perkin-Elmer 141 automaticpolarimeter. Light petroleum refers to the fractionhaving b.p. 40-60'.sulphonyl-u-D-allofuranose (5) .-The monoacetal (4)(1.65 g) in dry pyridine (20 ml) was treated overnight a troom temperature with toluene-p-sulphonyl chloride (3 g)in dry pyridine (20 ml); t.1.c. (light petroleum-ethyl, RO O-CMe2 bsol; HO o-me2 measured with a Perkin-Elmer R-10 spectrometer for6-Deoxy- 1,2-O-isoPropylidene-3-C-methyl- 5-O-p-tolyl-H r O M eMe OHacetate, 4 : 1) then showed that no starting materialremained. Work-up in the usual manner gave a syrupthat crystallised.Recrystallisation from ether-lightpetroleum gave the sulphonate (5) (2.65 g, 94), m.p.76.5-78.5", a, +27O (G 1.5 in CHCl,) (Found: C, 54.8;H, 6.5; S, 9.1. C,,H,,O,S requires C, 54.8; H, 6.5; S, _ _ _ _ .SCHEME Reagents: i, BzC1-C,H,N; ii, TsCl-C,H,N; iii, 8'6); 7 2-34 (4H, m, aromatic), 4-31 (1H, d, J i . 2 4 Hz,NaOMe-MeOH; iv, DBU; v, LiAlH,; vi, PhCH,Br-Me,N* H-1), 5.88 (lH, d, Jz,l 4 Hz, H-2), 7.54 (3H, s, ArMe), 8-46,8.64, and 8.80 (gH, each s, HOCMe and CMe,), and 8.59ix, Pd-C-H,; x, M-H,SO,.CHO-NaH; vii, MeOH-HCl; viii, MeI-Me,N*CHO-NaH;(3H, d, J5,6 6 Hz, HCMe).5-O-Benzoyl- 6-deoxy- 1 , 2-O-isopropylidene-3-C-methyZ-p-~- debenzylation Of the talofuranose (6).-A solution of the sulphonate (5) (2.5 g)(22) furnished 6-deoxY-2-0,3-C-dimethY1-a~-L- in NN-dimethylformamide (40 ml) containing sodiumtalofuranoside (23), which liberated 6-deoxy-2-0,3-C-methyl-L-talose (24) on hydrolysis with dilute sulphuric zz"4";g.~ s.Yamazaki~ and J- Yoshimura* Tetrahedronl1 J. S. Brimacombe, B. D. Jones, M. Stacey, and J . J. Willard, 13 E. Merck A.G., ' Chromatography,' Darmstadt, 2nd edn.,Cuvbohydvate Res., 1966, 2, 167. p. 301975 1295benzoate (5 g) was heated a t 140 "C for 18 11, whereaftert.1.c. (light petroleum-ethyl acetate, 4 : 1) showed that atleast three products had been formed. Water (50 ml) wasadded and the solution was extracted with methylenechloride (3 x 100 ml) . The combined extracts were dried(MgSO,) and concentrated to a syrup (1.8 g), and theresidue was chromatographed on silica gel (elution withlight petroleum-ethyl acetate, 4 : 1).The third componenteluted was the benzoate (6) (0.1 g, ca. 5), m.p. 136-137"(from ether-light petroleum), u, ca. 0" (c 0-6 in CHCl,)(Found: C, 63.6; H, 7.0. C,,H2,06 requires C, 63.4;.I2,, 4 Hz, H-2), 8.37, 8.61, and 8-73 (9H, each s, HOCMeand CMe,), and 8-55 (3H, d, 1 5 . 6 6 Hz, HCMe).1,2-O- Isopropylidene- 3-C-methyE-5,6-di-O-p-tolylsul~honyl-u-D-allofuranose (7).--The monoacetal (3) (11 g) in drypyridine (150 ml) was treated over 2 days a t room tem-perature with toluene-p-sulphonyl chloride (22 g) in drypyridine (150 ml), whereafter t.1.c. (light petroleum-acetone, 2 : 1) showed that the reaction was complete.Work-up in the usual manner gave the disulphonate (7)(21 g, 82y0), m.p.132-133" (from chloroform-lightpetroleum), a, +2l0 (c 1.5 in CHCl,) (Found: C, 52-8;H, 5.4; S, 11.6. C,,H,oO,oS, requires C, 53.1; H, 5.5;2 x ArMe), and 8-46, 8.65, and 8.77 (9H, each s, HOCMeand CMe,).Reaclion of 1,2-0- Isopropylidene-3-C-methyl-5,6-di-O-p-tolylsulphonyl-a-~-alloficranose (7) with Sodium Benzoate anNN-Dimethyl$ormamide.-A solution of the disulphonate(3-5 g) in NN-dimethylformamide (85 ml) containing sodiumbenzoate (10 g) was heated a t 150 "C for 20 h ; t.1.c. (lightpetroleum-acetone, 3 : 1) then showed the formation of twoproducts as well as the presence of a little starting material.The solution was diluted with ethyl acetate and filtered toremove inorganic material, and the solvents were removed.The residue was taken up in methylene chloride and theorganic extract was washed with water (3 x 250 ml), dried(MgSO,) , and concentrated t o a syrup.Chromatographyon silica gel (elution with light petroleum-acetone, 3 : 1)gave first 5,6-di-O-benzoyl- 1,2-O-isoproPylidene-3-C-methyl-P-L-talofzwanose (10) (0-94 g, 33), m.p. 158.5-159.5"(from methylene chloride-light petroleum) , u, - 28"(c 1.1 in CHCl,), vmx. 1710 cm-1 (benzoate) (Found: C,65.2; H, 6.1. C,4H2e08 requires C, 65.2; H, 5.9); Tca. 2.20 (lOH, m, aromatic), 4.1 1 (lH, d, Jl,, 4 Hz, H-l),and 8-38 and 8-62 (9H, each s, intensity ratio 1 : 2, HOCMeand CMe,) . Continued elution furnished 6-O-benzoyl- 1,Z-O-iso~ropylidene-3-C-methyl-~-~-talofuranose (1 1) (0-53 g,247(,), m.p.11 1-1 12" (from methylene chloride-lightpetroleum), a, +6" (c 0.2 in CHCl,), vmax. 1710 (benzoate)and 3400 cm-l (OH) (Found: C, 60.5; H, 6.7. C17H220,requires C, 60.4; H, 6.5); T ca. 2.12 (5H, m, aromatic),4.10 (lH, d, Jl,z 4 Hz, H-l), and 8-41, 8.63, and 8.67 (9H,each s, HOCMe and CMe,). Benzoylation of the mono-benzoate (11) transformed it into the dibenzoate (10)(identified by m.p. and mixed m.p.).furanose (13).-A cooled (ca. 0 "C) solution of benzoylchloride (8-5 g) in dry pyridine (50 ml) was added to acooled solution of the monoacetal (3) (13.3 g ) in dry pyridine(100 ml) and the mixture was stored at room temperaturefor 3 h ; t.1.c. (light petroleum-acetone, 2 : 1) then showedthe formation of two products and the presence of a littlestarting material.The solution was processed in theH, 6.8); T 4.09 (lH, d, J1.2 4 Hz, H-l), 5.78 (lH, d,S, 11.80,/0); T 4.37 (lH, d, Jl,Z 4 Hz, H-l), 7-52 (6H, S,6-O-Benzoyl- 1 , 2-O-isopropylidene-3-C-methyl-a-~-allo-usual way, and the resulting syrup was chromatographedon silica gel (elution with light petroleuni-acetone, 2 : 1)to give first the 5,6-dibenzoate (12) (10.9 g, 43), m.p.155.5-156" (from methylene chloride-light petroleum),a, +41" (c 0.9 in CHCl,), vmx. 1710 cm-l (benzoate)(Found: C, 65.4; H, 5.85. C,,H,,O, requires C, 65.2; H,5.9); T ca. 2.20 (lOH, m, aromatic), 4.18 (lH, d, J1.,4 Hz, H-1), and 8.42, 8.65, and 8.69 (9H, each s, HOCMeand CMe,). Continued elution afforded the inonobenzoate(13) (9 g, 47y0), m.p.112.5-113.5" (from methylenechloride-light petroleum), a, +ZS" (c 3 in CHCl,), vmx.1710 (benzoate) and 3420 cm-' (OH) (Found: C, 60.6; HI6-4. C17H2307 requires C, 60-4; H, 6.5) ; 7 ca. 2-12 (5H,m, aromatic), 4-24 (lH, d, Jl., 4 Hz, H-1), and 8.46 and8.68 (9H, each s, intensity ratio 1 : 2, HOCMe and CMe,).6-O-Benzoyl- 1,2-O-isoPropylidene- 3-C-methyl-5-O-p-tolyl-sulphonyl-u-D-dlofuranose (15) .-A solution of the mono-benzoate (13) (5.5 g) in dry pyridine (75 ml) was treatedovernight a t room temperature with toluene-p-sulphonylchloride (17.5 g) in dry pyridine (75 ml), whereafter t.1.c.(light petroleum-acetone, 3 : 1) showed that the reactionwas complete. Work-up gave the diester (15) (5-3 g, 66),m.p. 137-138" (from methylene chloride-light petroleum),u, +45" (c 1-1 in CHC1,) (Found: C, 58.7; H, 5-8; S, 7.0.C,4H280,S requires C, 58.5; H, 5.7; S, 6.5); 7 ca. 2.37(9H, m, aromatic), 4.28 (lH, d, J,,, 4 Hz, H-l), 7.65 (3H,s, ArMe), and 8.47 and 8.64 (9H, each s, intensity ratio 1 : 2,HOCMe and CMe,).1 , 2-O-Isopropylidene-3-C, 6-O-dimethyl-P-~-talo furanose(18).-The diester (15) (1 g) in dry chloroform (5 ml) wascooled to ca.-25 "C and treated with cold methanolicM-sodium methoxide (7.5 ml) ; afterwards the solution wasstored for 10 h a t room temperature, and t.1.c. (lightpetroleum-acetone, 4 : 1) then showed the formation of aproduct of lower mobility than the starting material.Solid carbon dioxide was added to neutralise the base andthe solvent was then removed.The residue was extractedwith ether, and the extract was filtered and chromato-graphed on silica gel (elution with light petroleum-methanol,7 : 1) to give the methyl ether (18) (0.3 g, 59.5y0), b.p.85-90" (bath) a t ca. 0.2 mmHg, u, + 11" (c 0.5 in CHC1,)(Found: C, 52.3; H, 8.35. C,,H,,O, requires C, 53.2; HI4 Hz, H-2), 6.54 (3H, s, OMe), and 8.38, 8-62, and 8.73(9H, each s, HOCMe and CMe,).1,2-0- Iso~ro~ylidene-3-C-met~~yl-5-O-p-tolylsul~honyl-u-~-allofuranose (16).-A solution of the diester (15) (5-2 g) indry chloroform (30 ml) was cooled to ca. -25 "C andtreated with cold methanolic M-sodium methoxide (40 ml) ;after 30 min, t.1.c. (light petroleum-acetone, 3 : 1) revealedthe formation of a single product of slightly lower mobilitythan the starting material.The solution was worked up(as before) and the resulting syrup was chromatographedon silica gel (elution with light petroleum-acetone, 3 : 1)to give the tosylate (16) (3-6 g, 88yo), m.p. 78-5-79-5"(from methylene chloride-light petroleum), u, + 18" (c 0.9in CHCl,) (Found: S, 8.0. C,,HZ4O,S requires S, 8.3);T 2.28 (4H, m, aromatic), 4.35 (lH, d, J,,, 4 Hz, H-l),7.54 (3H, s, ArMe), and 8.43, 8.68, and 8-78 (9H, each s,HOCMe and CMe,).furanose (17).-Method (a). To a cooled (- 25 "C) solutionof the sulphonate (16) (0.95 g) in dry chloroform (10 ml)was added methanolic M-sodium methoxide (15 ml) and,after 2 h, the mixture was worked up, as previously8*1yo); T 4.13 (lH, d, J1.2 4 Hz, H-l), 5.78 (lH, d, Jz,l5,6-A nhydro- 1,2-0-iso~ropylidene-3-C-methyl-~-~-taloJ.C.S.Perkin Idescribed, to give a syrupy residue (0-35 g). Chromato-graphy on silica gel (elution with light petroleum-acetone,3: 1) gave the anhydro-sugar (17) (80 mg, 15y0), m.p.129-130" (from methylene chloride-light petroleum),identical with that described below.A solution of the sulphonate (16) (1.94 g) inanhydrous benzene containing 1,5-diazabicyclo5.4.Oundec-5-ene (0.8 g) was heated under reflux for 2 h, whereaftert.1.c. (light petroleum-acetone, 3 : 1) showed the formationof a product having higher mobility than the diester (15).The solvent was removed and the residue was extractedwith methylene chloride (50 ml), which was washedalternately with M-sulphuric acid (2 x 20 ml) and sodiumhydrogen carbonate solution (2 x 20 ml) ; the combinedwashings were further extracted with methylene chloride(2 x 100 ml).The combined organic extracts were dried(Na,SO,) , decolourised (charcoal), and concentrated to givethe anhydvo-sugar (17) (0.95 g, 87), m.p. 129-130" (frommethylene chloride-light petroleum), a, +30" (c 0.7 inCHC1,) (Found: C, 55.9; H, 7.5. C10H1606 requires C,d, J2,1 4 Hz, H-2), and 8-43, 8-63, and 8.68 (9H, each s,HOCMe and CMe,).6-Deoxy- 1,2-O-~so~ropyl~dene-3-C-methy~-~-~-talofuvanos6(19).-Lithium aluminium hydride (1-2 g) was added inportions t o a stirred solution of the anhydro-sugar (17) (3 g)in dry ether (200 ml) and, after 30 min, more ether (500 ml)was added, followed by ethyl acetate to destroy the excessof hydride.Concentration of the dried (MgSO,) ethereallayer gave the 6-deoxy-sugar (19) (2.5 g, 83), m.p. 112.5-113O (from methylene chloride-light petroleum), a, + 14'(c 2 in CHC1,) (Found: C, 65.3; H, 8-6. CIoH18OS requires(lH, d, J2,1 4 Hz, H-2), amp;42, 8.64, and 8.83 (9H, each s,HOCMe and CMe,), and 8.76 (3H, d, J5,6 6 Hz, HCMe).Benzoyl chloride (0.07 ml) was added carefully to acooled (0 "C) solution of the 6-deoxy-sugar (19) (90 mg) indry pyridine (2 ml), and the mixture was kept for 1 h a troom temperature; t.1.c. (light petroleum-acetone, 3 : 1)then showed that all the starting material had reacted.Work-up in the usual manner and chromatography on silicagel (elution with light petroleum-acetone, 5 : 1) furnishedthe benzoate (6) (0.1 g), m.p.136-136-5' (from ether-lightpetroleum), a, ca. 0" (c 0.2 in CHC1,). The n.m.r. spectrumof this compound was indistinguishable from that preparedpreviously and no depression of m.p. was observed onmixing the samples.3,5-Di-O-benzyl-6-deoxy- 1,2-O-isopropylidene-3-C-methyl-P-L-talofuranose (20).-Sodium hydride (2 g) was added insmall portions to a stirred and cooled (0 "C) solution of thediol (19) (2 g) in NN-dimethylformamide (25 ml) and, afterthe gradual addition of benzyl chloride (4 ml), the mixturewas stirred for 4 h a t room temperature; t.1.c. (lightpetroleum-acetone, 3 : 1) then showed that no startingmaterial remained. Methanol was added to destroy theexcess of reagent and the solvents were removed.Theresidue was extracted with methylene chloride (150 ml),and the extract was filtered, washed with water (3 x 100ml), and dried (MgSO,). Removal of the solvents left asyrup (4.4 g) that was chromatographed on silica gel(elution with light petroleum-acetone, 9 : 2) to give thedibenzylated cpmpound (20) (2.4 g, 66), b.p. 140-145'(bath) a t ca. 0-05 mmMg, a, +27" (G 0.4 in CHC1,) (Found:C, 72.5; H, 7.5. C24H3005 requires C, 72.4; H, 7.5);z 2.59 (lOH, s, aromatic), 4-27 (4H, q, 2 x PhCH20), 4.47Method (b).55.6; HI 7.4); z 4.13 (lH, d, J1,2 4 Hz, H-1), 5.80 (lH,C, 55.0; H, 8.3); T 4.18 (lH, d, J1.2 4 Hz, H-1), 5.83(lH, d, J1.2 4 Hz, H-1), 5-97 (lH, d, J S . 1 4 Hz, H-2), 8.38,8.63, and 8.76 (9H, each s, PhCH,OCMe and CMe,), and8.74 (3H, d, J 5 , 6 6 Hz, HCMe).Methyl 3,5-Di-O-benzyl- 6-deoxy-2-0,3-C-dirnethyl-a- andp-L-talofuvanosides (22) .-The benzylated acetal (20) (0.96 g )was methanolysed in refluxing methanolic 2.5 hydrogenchloride (80 ml) during 1.5 h.The solution was neutralised(PbCO,) and filtered, and the filtrate was concentrated tofurnish a syrupy ap-mixture (0.89 g) of the glycosides (21).Sodium hydride (0.5 g) was added in portions to a cooled(0 "C) and stirred solution of the glycosides (0.89 g) inNN-dimethylformamide (60 ml) , whereupon methyl iodide(2.5 ml) was added carefully and the mixture was stirredfor 2 h a t room temperature. Methanol was then addedto destroy the excess of reagents and the solution was con-centrated. The residue was extracted with methylenechloride (225 ml), which was washed with water (3 x 75 ml)and dried (Na,SO,).Removal of the solvent left a syrupymixture of the methylated a- and P-glycosides (22) (0.94 g,ca. looyo), which was suitable for the next stage of thesequence. However, in one instance, chromatography onsilica gel (elution with light petroleum-acetone, 6 : 1) gavethe methylated glycoside of higher mobility in pure form;it had b.p. 125-130" (bath) a t ca. 0.05 mmHg, ab 3-14'(c 0.5 in CHCl,); T 2.57 (lOH, s, aromatic), 4-93 (lH, d,J1,2 3 Hz, H-l), 5.32 and 5.41 (q and s, intensity ratio 1 : 1,2 x PhCH,O), 6.52 (6H, s, 2 x OMe), 8.63 (3H, s,PhCH,OCMe), and 8.71 (3H, d, J6,* 6 Hz, HCMe) (Found:C, 70.6; HI 7.7. C2,H3,O6 requires C, 71.5; H, 7.8).Funabashi et uZ.l2 record a, -3.4" (G 1 in MeOH) forthe more mobile a-(22) and a, +66" (c 1 in MeOH) forMethyl 6-Deoxy-2-0,3-C-dimethyl-a- and -P-L-taEofurano-sides (23).-A solution of the a- and P-glycosides (22)(0.61 g) in methanol (30 ml) containing 5 palladisedcharcoal (0.6 g) was shaken with a slight overpressure ofhydrogen for 2 h at room temperature; t.1.c.(lightpetroleum-acetone, 3 : 1) then showed that no startingmaterial remained. The catalyst was filtered off and thefiltrate was concentrated to a syrup containing the debenzyl-ated a- and p-glycosides (23) (0.32 g, 98), which wassuitable for the next stage of the sequence. However, inone instance, chromatography on silica gel (elution withlight petroleum-acetone, 2 : 1) gave the GomponePat ofhigher mobility in pure form; b.p.55-60' (bath) a tGU. 0.05 mmHg, a, ca. 0" (c 0.6 in CHC1,) (Found: C,52.4; H, 9.0. C,H180, requires C, 52.4; H, 8.7) ; z 5.01(lH, d, J1,, 3 Hz, H-1), 6-44 (6H, s, 2 x OMe), 8-59 (3H, s,HOCMe), and 8.74 (3H, d, J 5 , 8 6 Hz, HCMe). Funabashiet al.12 report aID24 - 15" (c 1.3 in MeOH) for the a-anomer.6-Deoxy-2-0,3-C-diunethyI-~-talose ( Vinelose) (24) .-Asolution of the a- and Pglycosides (23) (0.32 g) in ethanol(2 ml) and M-sulphuric acid (6 ml) was heated for 2 h on aboiling water-bath, during which time complete hydrolysisoccurred. The hydrolysate was neutralised (BaCO,) andthe filtered solution was concentrated. Chromatographyof the syrupy residue on silica gel (elution with lightpetroleum-acetone, 3 : 1) gave vinelose (24) (0.2 g, 67y0),+13" (c 0.7 in H,O), as a syrup which could not beinduced to crystallise (lit.,6 a5a6 + 12" (c 1 in H,O)).Themass spectrum of the syrupy product was in agreementwith that published and accurate measurement of thehighest peak (M+' - 18) gave a value of un/e 174-0889(CaH140, requires 174.0892). The i.r. spectrum (KBr disc)of t h e synthetic material was indistinguishable from thatP- (22) 1975published for the branched-chain sugar derived fromnatural sources. Paper chromatography and paper electro-phoresis (see Table) confirmed the identity of the syntheticmaterial with vinelose.Paper chromatographic and paper electrophoretic propertiesof 6-deoxy-2-0,3-C-dimethyl-~-talose (24) and naturalL-vineloseChromatography 0r A , Electro-Vinelose A B C D E phoresisbSynthetic 0.79 0.82 0.77 0.79 0.79 9.6Natural 0.79 0-82 0.77 0.79 0.79 9.5a Rp Values in A, ethyl acetate-acetic acid-water, 3 : 1 : 3;B, pyridine-ethyl acetate-water, 1 : 3 : 1-15; C .butan-l-ol-ethanol-water, 4 : 1 : 5; D, butan-l-ol-pyridine-water,6 : 4 : 3 ; and E, butan-l-ol-pyridine-0~05~-morpholiniumtetraborate (pH 8.6), 7 : 6 : 2. Both samples gave a pink colourwith vanillin-perchloric acid, which showed a change togreenish blue within 24 h. b Movement towards anode (cm) in0.lM-sodium tetraborate (pH 9.8) at 30 V cm'l for 76 mh.6-Deo.~y-2-0,3-C-dirnethyl-~-talitol ( Vinelitol) (25) .-Sodium borohydride (0.62 g) was added to a solution ofvinelose (24) (0.17 g) in O-O05~-sodium carbonate (100 ml)and the mixture was set aside overnight at room tem-perature. The solution was then deionised by passagethrough Amberlite IR-120 (H+) resin, and the effluent andwashings were concentrated to a syrup, with repeatedadditions of methanol. The residue was chromatographedon silica gel (elution with light petroleum-acetone, 2 : 1) togive vinelitol (0.1 g), a546 -6O (c 0.5 in H20) (lit.,6 aa4s-6.4" (c 1 in H,O)}. The n.m.r. spectrum (D20) of thematerial so obtained was indistinguishable from thatpublished 5 for the alditol derived from natural vinelose.1,4,5-Tri-O-acetyl-6-deoxy-2-0,3-C-dimefhyZ-~-talitol (26).-Acetylation of vinelitol (25), according t o the literatureprocedure,5 afforded the triacetate (26), a546 -41' (c 0.9 inCHCl,) {lit.,5 a548 -446" (c 1 in CHCI,)), whose n.m.r.spectrum (CDCl,) was identical with that published.We thank Professor S. Suzuki and Dr. S. Okuda forcomparing the synthetic sugar with natural vinelose, andDr. R. K. Mackie, University of St. Andrews, for the massspectral data. Grants from the S.R.C. (to S. RI.) and theUniversity of Dundee (to A. J. R.) in support of this workare gratefully acknowledged.6/092 Received, 16th Januavy, 1976