摘要:
The BF3.Et2O-promoted addition of racemic alpha- and gamma-alkoxyallylstannanes 2 or 3 to the 2-methoxyoxazolidine 1 afforded adducts 4 and 5 in diastereomeric ratios up to 95:5 accompanied by enantioenriched gamma-stannanes (R)-3. This behavior is consistent with a fast alpha-to-gamma rearrangement of the alkoxystannanes followed by an enantiomer- as well as mutual diastereoface-discriminating condensation.