SYNTHESIS OF INHIBITORS OF 2,3-OXIDOSQUALENE LANOSTEROL CYCLASE .2. CYCLOCONDENSATION OF GAMMA,DELTA-UNSATURATED BETA-KETO-ESTERS WITH IMINES

Synthesis and the biological evaluation of ammonium ion analogues of the first carbocyclic cationic intermediate 4 presumed to formed during the cyclization of 2,3-oxidosqualene to protosterol, 2, by 2,3-oxidisqualene-lanosterol cyclase (OSC) is presented. Preparation of the required 4-hydroxy-2,3-substituted-4-piperidine 12 (and its corresponding methiiodide salt 13) involved, as a key step, cyclocondensation of imine 17 with methyl 2-methyl-3-oxo-4-pentenoate (16) to give C-2,C-3-substituted 4-piperidone 15 as a single diastersoisomer. Subsequent elaboration to give 13 was accomplished in six steps in an overall yield of 50%. Analogue 12 inhibited 2,3-oxidosqualene-lanosterol cyclase of Candida albicans with an IC50 of 0.23 muM.