Transformation of the (2-nitrophenyl)acetyl protecting group in the presence of trichloroacetonitrile and 1,8-diazabicyclo[5,4,0]-undec-7-ene.

When treated with trichloroacetonitrile in the presence of 1,8-diazabicyclo[5,4,0]-undec-7-ene, the (2-nitrophenyl)acetyl protecting group (NPAc) was partially transformed into mono-(NPClAc) and dichlorinated (NPCl₂Ac) species, but no chlorination occurred in the presence of solid potassium carbonate. The monochlorinated NPClAc group, which is suitable for use in glycosylation reaction, can be selectively removed by treatment with thiourea.