The morita-baylis-hillman reaction of chiral highly oxygenated cyclopent-2-enones

The Morita-Baylis-Hillman (MBH) reactions of (4S,5R,7R,8R)- and (4R,5R,7R,8R)-4-hydroxy-7,8-dimethoxy-7,8-dimethyl-6,9-dioxaspiro[4.5] dec-2-en-1-ones (2 and 3, resp.) with aldehydes using various catalysts were studied. A combination of Bu ₃P/phenol in THF was found being optimum conditions giving the corresponding MBH adducts with high diastereoisomeric ratios. After separation, each stereomerically pure isomer of the MBH adducts was subjected to hydrolysis employing 1% aq. CF ₃COOH (TFA) in a water bath of an ultrasonic cleaner to afford the corresponding polyhydroxylated cyclopentenones in good yields.