Preparation of new (4aRS,5SR,9bSR)- and (4aRS,5SR,9bRS)-1,3,4,4a,5,9b-hexahydro-5-phenyl-2H-indeno 1,2,c - pyridines of formula (I) is effected by the following schemes: (R1=R11=lower alkyl, alkenyl or alkynyl) X = acid residue of a reactive ester cyclising to I cyclising with polyphosphoric acid to I (R1II=R1=H, lower alkyl or alkenyl; R3=R2) reduction with lithium aluminium hydride right arrow I (R1=H or lower alkyl) aluminium hydride or diborane Ie (R1 = H, lower alkyl or alkoxy) (hydrogenolytic) right arrow I (R1 = H) splitting (R4 = methyl or benzyl) or heating a cpd. (4aRS,5SR,9bRS) of formula (I) in alkaline medium to obtain a cpd. (4aRS,5RS,9bRS) of formula (I) and desirably separating the mixture of (4aRS,5SR,9bSR) and (4aRS,5SR,9bRS) cpds. into their isomers. In the formulae either R1, R2 and R3 stand for H or R1 is H, lower alkyl, alkenyl or alkynyl or has a limited meaning as given in brackets uner specific formulae, R2 is Cl, Br, F or lower alkyl and R3 is H, Cl, Br, F or a lower alkyl, alkylthio- or alkoxy gp. or trifluoromethyl.
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