SYNTHESIS OF (1R,CIS,ALPHA-S)-CYPERMETHRINE VIA LIPASE-CATALYZED KINETIC RESOLUTION OF RACEMIC M-PHENOXYBENZALDEHYDE CYANOHYDRIN ACETATE

A technical scale preparation of optically active (1R,cis,alpha S)-cyp ermethrine 4 from racemic m-phenoxybenzaldehyde cyanohydrin acetate (R S)-1 and s)-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane- carboxylic acid chloride (1R,cis)-3 is described. Key steps of the new procedure are a lipase catalyzed enantioselective transesterification of (RS)-1 with n-butanol and direct acylation of the mixture of (R)-1 and (S)-c yanohydrin (S)-2 with (1R,cis)-3 to give enantiomerically pure (1R,cis ,alpha S)-4. The unchanged (R)-1 is removed from (1R,cis,alpha S)-4 by distillation, and is racemized with triethylamine to give (RS)-1 whic h is returned to the process. The total yield of (1R,cis,alpha S)-4 re ferred to (RS)-1 is 80%. (C) 1998 Elsevier Science Ltd. All rights res erved.