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The o-phenazophenoxyacety] moiety has been found to be an effective amino-protecting group for several amino esters. It can be introduced via acylation of the amino ester with an appropriate carboxylic acid. The removal of this blocking group was easily accomplished by reduction of the azo portion using potassium borohydride and palladium on carbon followed by acidification of the reaction mixture. An intramolecular rearrangement occurred which was followed by fragmentation into a benzoxazinone and the regenerated amino ester. Both the introduction and removal of this amino-protecting group were completed in higher yields than those obtained in previous procedures which employed the o-nitrophenoxyacetyl blocking group.

Abstract:The infrared spectroscopic investigations for the =CH and NH vibrations and the effect of substitution at different positions in the phenyl rings of 2-amino-4,6-diphenyl-3,6-dihydropyrimidines have been described. The CH stretchings were observed between 3070-3060 cmG 1 . The observed frequencies differ for -NH bending and the =CH and -CH stretching vibrations, and the difference between the two frequencies is larger than the predicted differences between scaled frequencies. It has been observed that the substitution of phenyl rings with -OH, -OCH 3 , -NO 2 and -Cl groups, further complicated the elucidation of the spectra. The electronic transitions in the UV spectra were observed to be hypsochromic (blue shift) when a powerful electron donor group is present in the heterocyclic nucleus. Other electronic transitions were observed in the ultraviolet spectra to check the presence of B-B * and n-* transitions in these compounds.

Methyl 2,2‐di‐O‐methyl‐6‐C‐methyl‐α‐D‐gulopyranoside has been synthesized from D‐glucose. The introduction of methyl branching at 3‐position was achieved by the Grignard reaction.