Efficient synthesis of rare sugar D-allal via reversal of diastereoselection in the reduction of protected 1,5-anhydrohex-1-en-3-uloses: protecting group dependence of the stereoselection.
D-allal was selectively obtained by reducing bulky-silyl-protected 1,5-anhydrohex-1-en-3-uloses using the NaBH4CeCl3 x 7 H2O system. The crucial point of this synthesis is the nature of the protecting group. When bulky silyl group such as t-butyldiphenylsilyl was used as substrate, protected D-allal was obtained in >99% selectivity. In contrast, when acetylated enone was used, protected D-glucal was obtained exclusively. The addition of CeCl3 x 7 H2O was also found to influence selectivity.
Fujiwara
Takashi
T
Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe 657-8501.
Hayashi
Masahiko
M
D006601:Hexoses / Q000138:chemical synthesis* / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D013379:Substrate Specificity
D006601:Hexoses