ABSTRACT
Reductive ring openings of 3-O-benzoyl-4,6-O-benzylidene-D-glucopyranosides with BH(3)·NMe(3)-AlCl(3) are accompanied by side reactions, such as debenzoylation and reduction of the benzoate to benzyl ether. This phenomenon was rationalized by aluminium chelate formation between the O-4 acetal and the benzoyl carbonyl group oxygens. It was also shown that these side reactions can be eliminated by using BH(3)·THF as the reducing agent.
Subject(s)
Acetals/chemistry , Benzylidene Compounds/chemistry , Boranes/chemistry , Monosaccharides/chemistry , Aluminum Chloride , Aluminum Compounds/chemistry , Aluminum Compounds/metabolism , Carbohydrate Conformation , Chelating Agents/metabolism , Chlorides/chemistry , Chlorides/metabolism , Indicators and Reagents/chemistry , Magnetic Resonance Spectroscopy , Methylamines/chemistry , Oxygen/metabolism , Reducing Agents/chemistry , StereoisomerismABSTRACT
The utility of the (2-nitrophenyl)acetyl (NPAc) group for the protection of hydroxyl functions is reported. (2-Nitrophenyl)acetates are readily prepared starting from the commercially available, inexpensive (2-nitrophenyl)acetic acid, and these esters are stable under a series of common carbohydrate transformations. The NPAc group can be removed selectively using Zn and NH(4)Cl without affecting a series of common protecting groups. This new protecting group is orthogonal with the commonly used tert-butyldimethylsilyl, levulinoyl, 9-fluorenylmethoxycarbonyl, naphthylmethyl, and p-methoxybenzyl groups.
