General Route to 2,4,5-Trisubstituted Piperidines from Enantiopure β-Amino Esters. Total Synthesis of Pseudodistomin B Triacetate and Pseudodistomin F
作者:Dawei Ma、Haiying Sun
DOI:10.1021/jo000447q
日期:2000.9.1
The Michael addition reaction of enantiopure beta-amino esters with methyl acrylate followed by Dieckmann condensation and enol silylation affords the enol ethers 6, which are hydrogenated with catalysis by Raney-Ni at 80 atm and 80 degrees C to provide 2,4, 5-trisubstituted piperidines with high diastereoselectivity. In this case Ni-H attacks the C-C double bond from the direction of the 2-alkyl group
Psuedodistomins A and B, piperidine alkaloids isolated from the Okinawan tunicate Pseudodistoma kanoko, have been synthesized as their racemic acetates via a route involving Grignard coupling reaction to provide unambiguous proof of their structures.
Pseudodistomin C, a new cytotoxic piperidine alkaloid, was isolated from the Okinawan tunicate Pseudodistoma kanoko and the structure elucidated by spectral data, chemical degradations, and synthesis. The absolute configurations of the C-4 and C-5 chiral centers of pseudodistomin C were revealed by chiral HPLC analysis to be 4S and 5R, which were opposite to those of pseudodistomins A and B, previously isolated from the same tunicate, having the same planar structure as to the piperidine nucleus.