Enantioselective Synthesis and Absolute Configuration Assignment of Gabosine O. Synthesis of (+)- and (−)-Gabosine N and (+)- and (−)-Epigabosines N and O

[reaction: see text] A rational approach to the synthesis of gabosines and other related carba-sugars starting from a masked p-benzoquinone has been designed. The enantioselective acetylation of the hydroxyketal 2 provides a practical entry to either enantiomer of the target products. The strategy has been applied to the synthesis of (+)- and (-)-gabosines N and O and (+)- and (-)-epigabosines N and O. The absolute configuration of natural gabosine O has been established.