Enzymatic route to chiral, nonracemic cis-2,6- 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 synthesis of 2-alkyl-6-methylpiperidines is presented via the enzymatic desymmetrization of meso cis-2,6- and cis,cis-2,4,6-substituted piperidines with Aspergillus niger lipase(ANL). The enzymatic reaction proceeds in excellent chemical yield and high enantiotopic selectivity (ee greater than or equal to 98%). The general method is used to effect the synthesis of (+)-dihydropinidine-HCl as well as the first asymmetric synthesis of dendrobate alkaloid (+)-241D.