The addition of 5-methyl-2-triisopropylsilyloxyfuran (5) to N-carbobenzyloxy-2-methoxypiperidine (6a) afforded a mixture of the corresponding erythro and threo isomers 7a and 8a, respectively, in moderate to good yields (42-85%) and diastereoisomeric ratio (7a : 8a) ranging from 1.1:1 _ 6:1 depending on the solvent system and the Lewis acid employed. The threo isomer 8a was eventually converted to (+/-)-homopumiliotoxin 223G (1) which was prepared in 5 steps and 13% overall yield from 6a.
homopumiliotoxin 223G; N-acyliminium ions; silyloxyfuran; vinylogous addition
