Methanol reaction with glucose

Reaction of glucose with methanol and gaseous HCl yields four acetal products, the a- and P-pyran-osides and a- and P-furanosides, which may be separated. The pyranosides are the predominant components, and the major product is the a-pyran-oside. This is perhaps unexpected, in that the P-pyranoside has ah its substituents equatorial. 

Under basic conditions, the thiourethano group also reacted by displacement by the nitrogen atom. The D-glucose compound (212), on reaction with methanolic sodium methoxide at room temperature, gave ... 

In the experiments first described, 2-amino-2-deoxy-D-glucose was heated with an excess of the /3-dicarbonyl compound in the absence of solvent. The product so obtained from ethyl acetoacetate, m.p. 142°, [a]n 49.7°, had an analysis corresponding to that for ethyl 2-methyl-5-(D-ara6mo-tetrahydroxybutyl)pyrrole-3-carboxylate and was considered to have this structure (1). In the reaction with 2,4-pentanedione, a material (m.p. 98°, Md — 25.1°) was obtained which was described as 3-acetyl-2-methyl-5-(D-ara5fno-tetrahydroxybutyl)pyrrole (2). Boyer and Furth" repeated the latter reaction, but in methanol solution, and obtained a product, m.p. 133°, whose analytical data were in agreement with those for structure (2). 

Monosaccharides can be modified by reaction with alcohols and amines to form adducts. For example, D-glucose will react with methanol in an acid-catalyzed process the anomeric carbon atom reacts with the hydroxyl group... 

Problem 18.44. In the reaction of methanol with glucose and fructose, why does reaction occur only at the hemiacetal and hemiketal OH groups instead of also occurring at the alcohol OH groups ... 

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