Asymmetric Synthesis of Polyhydroxylated Pyrrolizidines via Transannular Iodoamination with Concomitant N-Debenzylation

作者：Brock E Anne; Davies Stephen G^*; Lee James A; Roberts Paul M; Thomson James E

来源：Organic Letters, 2011, 13(7): 1594-1597.

DOI：10.1021/ol103090z

The doubly diastereoselective "matched" conjugate addition of lithium (R)-N-but-3-enyl-N-(alpha-methyl-p-methoxybenzyl)amide to tert-butyl (4S,5R,E)-4,5-O-isopropylidene-2,7-dienoate (derived from D-ribose in 3 steps) and in situ enolate oxidation with (-)-camphorsulfonyloxaziridine was followed by ring-closing metathesis with Grubbs 1 to give a hexahydroazocine scaffold. Subsequent treatment with I-2 resulted in transannular Iodoamination accompanied by loss of the alpha-methyl-p-methoxybenzyl group to give the corresponding pyrrolizidine scaffold as a single diastereoisomer upon direct crystallization from the crude reaction mixture. Further functional group manipulations enabled the preparation of (-)-7a-epi-hyacinthacine A1.

• 出版日期2011-4-1