ENZYMATIC ROUTE TO CHIRAL, NONRACEMIC CIS-2,6-SUBSTITUTED AND CIS,CIS-2,4,6-SUBSTITUTED PIPERIDINES - SYNTHESIS OF (-DIHYDROPINIDINE AND DENDROBATE ALKALOID (+)-241D())

Piperidine-based compounds are an important class of natural alkaloids found in plants, insects, and amphibians. A general asymmetric synthe sis of 2-alkyl-6-methylpiperidines is presented via the enzymatic desy mmetrization of meso cis-2,6- and cis,cis-2,4,6-substituted piperidine s with Aspergillus niger lipase(ANL). The enzymatic reaction proceeds in excellent chemical yield and high enantiotopic selectivity (ee grea ter than or equal to 98%). The general method is used to effect the sy nthesis of (+)-dihydropinidine-HCl as well as the first asymmetric syn thesis of dendrobate alkaloid (+)-241D.