Synthetic studies on swainsonine analogs

Abstract

We have investigated a new synthetic route to (-)-swainsonine and its analogs, which exhibited remarkable physiological effects including an immunoregulative activity. Iodoamination of γ-aminoalkene and allylic imidate was employed for the approach to their synthesis. However, the preparation of γ-aminoalkenes 45 and 56 was not so facile that iodocyclization of allylic imidate was prepared for the planned iodocyclization. Allylic alcohols 100A, 101A and 102A were readily derived from 79 which was obtained from Wittig olefination of lactol 78 and phosphonium salt 51B. Cyclization of allylic imidate of 100A, 101A and 102A was carried out in acetonitrile at 0℃-30℃ by using IBr as electrophile to furnish dihydrooxazole 100B, 101B and 102B, respectively. We made much efforts to convert the dihydrooxazole to (-)-swainsonine and its analogs, but successful results were not obtained.