Nitroso Dienophiles Synthesis of Azasugars

SCHEME 13.82 Jprgensen s asymmetric synthesis of an ethyl P-D-mannopyranoside derivative. 

SCHEME 13.83 Streith s synthesis of l,5,6-trideoxy-l,5-iminoalditols and aldonolactames. 

Methyl urazol 302 was oxidized into A-methyl triazoline-3,5-dione with tert-buiy hypochlorite. Without isolation, it was then reacted with ( )-penta-2,4-diene-l-ol giving adduct ( )-303 as a racemic mixture. On treatment of ( )-303 with a lipase (R/Novozym 435) in vinyl acetate, 38% of ester (5)-304 (86% ee) and 29% of alcohol (/ )-303 (59% ee) were isolated. Epoxidation of (5 )-304 

SCHEME 13.84 Defoin s synthesis of 2,5-iniino-2,5,6-trideoxy-D-altritol. 

SCHEME 13.85 Defoin s syntheses of 4-amino-4,5-dideoxy-L-lyxose derivatives. 

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