Asymmetric synthesis of polyhydroxylated pyrrolizidines via transannular iodoamination with concomitant N-debenzylation.

Journal article

The doubly diastereoselective "matched" conjugate addition of lithium (R)-N-but-3-enyl-N-(α-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 I to give a hexahydroazocine scaffold. Subsequent treatment with I(2) resulted in transannular iodoamination accompanied by loss of the α-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.

Authors: Brock, E; Davies, S; Lee, J; Roberts, P; Thomson, J

• Publication status: Published
• Journal: Organic letters
• Volume: 13
• Issue: 7
• Pages: 1594-1597
• Publication date: 2011-04-01
• DOI: 10.1021/ol103090z
• EISSN: 1523-7052
• ISSN: 1523-7060
• Language: English