Synthesis of 1,6‐Dideoxynojirimycin, 1,6‐Dideoxy‐ D ‐ allo ‐nojirimycin, and 1,6‐Dideoxy‐ D ‐ gulo ‐nojirimycin via Asymmetric Hetero‐ Diels‐Alder Reactions

Asymmetric Diels‐Alder reaction of sorbaldehyde O ‐methyloxime 1d with chiral chloronitroso derivative 2 of D ‐mannose, followed by osmylation of the primary cycloadduct, led to diol 6a with excellent enantioselectivity (ee > 99%; Scheme 1 ). Catalytic hydrogenolysis of 6a gave 1,6‐dideoxy‐ D ‐ allo ‐nojirimycin ( 7a ). Nucleophilic ring opening of cyclic sulfate 8 allowed a straightforward synthesis of 1,6‐dideoxynojirimycin ( 11 ) and of 1,6‐dideoxy‐ D ‐ gulo ‐nojirimycin ( 12 ; Scheme 2 ).