The development of two novel ring conversions of sugar derivatives is described. The first is an efficient conversion of 5-enopyranosides and 6-
O-acetyl-5-enopyranosides to the corresponding substituted cyclohexanones mediated by a catalytic amount of palladium dichloride. After a survey of various substrates, the reaction was confirmed to be general and useful. Syntheses of bioactive compounds utilizing this method were therefore investigated. Cyclophellitol, which is a potent β-glucoidase inhibitor, and its diastereoisomer were efficiently synthesized. Furthermore, novel synthesis of all enantiomerically pure diastereoisomers of inositol starting with 6-
O-acetyl-5-enopyranosides was investigated. Good accessibility of these enantiomerically pure inositol diastereoisomers results in the efficient syntheses of D-
myo-inositol 1,4,5-trisphosphate and D-
myo-inositol 1,3,4,5-tetrakisphosphate. The second investigation involved novel and efficient conversion of D-glycono-1,5-lactones into the corresponding L-sugars. The important intermediate, δ-hydroxyalkoxamate, was provided by a practical alkoxyamination of D-glycono-1,5-lactones mediated by Me
3Al. In contrast to the preparation of β-lactam skeletons from β-hydroxyalkoxamates, the cyclization of δ-hydroxyalkoxamates under Mitsunobu conditions resulted in O-alkylation rather than N-alkylation. It is noteworthy that δ-hydroxyalkoxamates derived from D-mannono-1,5-lactones afforded the
O-alkylation product in 91% yield. No
N-alkylation product was detected in this case. These
O-cyclized oximes, in which the inversion of the configuration at C5 was secured, were efficiently converted into L-sugars.
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