A catalytic one-step process for the chemo- and regioselective acylation of monosaccharides.
An organocatalytic method for the chemo- and regioselective acylation of monosaccharides has been developed. Treatment of octyl beta-D-glucopyranoside with isobutyric anhydride in the presence of 10 mol % of a C2-symmetric chiral 4-pyrrolidinopyridine catalyst (1) at -50 degrees C gave the 4-O-isobutyryl derivative as the sole product in 98% yield. Thus, chemoselective acylation, favoring a secondary hydroxyl group in the presence of a free primary hydroxyl group, and regioselective acylation, favoring one of three secondary hydroxyl groups, took place with perfect selectivity. A competitive acylation between octyl beta-D-glucopyranoside and a primary alcohol (2-phenylethanol) with 1.1 equiv of isobutyric anhydride in the presence of 1 gave the 4-O-isobutyrate of octyl beta-D-glucopyranoside with 99% regioselectivity in 98% yield, which indicates that acylation of the secondary hydroxyl group at C(4) of the carbohydrate proceeds in an accelerative manner. A possible mechanism, involving multiple hydrogen-bonding between 1 and the monosaccharide, is proposed for the chemo- and regioselective acylation.
Kawabata
Takeo
T
Institute for Chemical Research, Kyoto University, Uji, Kyoto, Japan. kawabata@scl.kyoto-u.ac.jp
Muramatsu
Wataru
W
Nishio
Tadashi
T
Shibata
Takeshi
T
Schedel
Hartmut
H
D002236:Carbohydrate Conformation; D002241:Carbohydrates / Q000737:chemistry; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods; D006860:Hydrogen Bonding; D006868:Hydrolysis; D008956:Models, Chemical; D015394:Molecular Structure; D009005:Monosaccharides / Q000737:chemistry*; D011714:Pyrans / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism
D002241:Carbohydrates; D009005:Monosaccharides; D011714:Pyrans; D012997:Solvents