Trichloroacetyl group removal

Little is known about transition metal catalyzed epoxidation of simple allylic amides. The easily removable trichloroacetyl group is suitable as /V-substituent in the molybdenum-catalyzed epoxidation of (Z)-allylic systems with rm-butyl hydroperoxide, which produces the. sv -com-pound with appreciable selectivity21. 

Tri-O-acetyl-a-D-glucopyranosyl azide (189), obtained from Brigl s chloride (3,4,6-tri-(9-acetyl-2-trichloroacetyl-p-D-glucopyranosyl chloride) by selective removal of the trichloroacetyl group has long been the only representative of this class of compounds. 

Synthesis from o-allose A synthesis of the (3-lactam 15 has been reported from the D-allose derivative 11 (Scheme 1). Silylation of 11 followed by treatment with trichloroacetyl isocyanate afforded after crystallization the (3-lactam 12 (50%). Benzylation of 12 afforded 13, which underwent removal of the protecting groups to give 14. Cleavage of the vicinal diol group in 14, with sodium metaperiodate under standard conditions, led to the formation of a dialdehyde, which without isolation was reduced to give the (3-lactam derivative 15. 

Pyridinium p-toluenesulphonate in methanol at reflux has been shown to be effective in selective removal of the isopropylldene groups of 1, 6-anhydro-2,3-0-isopropylidene-/d-D-mannopyrano3e derivatives bearing 4.-0-allyl, -tert-butyl, -trichloroacetyl, and -tert-butyldi-phenylsilyl groups. 

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