Acetobromo

Carbohydrate orthoesters, first reviewed by Pacsu more than 60 years ago [8], were reported by Fischer et al. [9] as by-products of the Koenigs-Knorr reaction [3] of acetobromo-L-rhamnose (1) with methanol. Orthoacetate 3 was isolated along with the expected a- and P-methyl rhamnosides 2 (Scheme 5.2). However, its true structure was assigned only 10 years later by several research groups [10-12]. 

The first glucuronides to be synthesized appear to have been those of phenol and euxanthone, which Neuberg and Neimann10 prepared by the action of the acetobromo derivative of D-glucuronolactone on the potassium salts of the phenols in methanolic solution. 

Recently, a total synthesis of salmochelin SX (70) has been reported which used cross-coupling of acetobromo-a-D-glucose 96 with arylzinc derivative 97 to furnish 98, followed by full deacylation and perbenzylation to give 99. Subsequent saponification of the methyl/benzyl ester, formation of the acid chloride, and addition of a protected L-serine unit yielded 100. Final deprotection formed the glucosyl-DHB-serine 70 in 28% overall yield (Fig. 17) [121]. This strategy involved the stepwise addition of the aryl moiety and serine (76a) to the sugar portion, which is in the opposite order to the biosynthetic rationale. 

It has been pointed out, with reference to Table II, that the strongly acidic conditions which are ordinarily employed to replace the Cl-acetoxy group of a sugar acetate by halogen have yielded only one of the two anomeric O-acetylglycosyl halides. In 1901, Fischer and Armstrong106 described diastereoisomers for the acetochloro and acetobromo derivatives of... 

Isbell and Frush10 have reported an extensive study of the reaction of a-acetobromo-D-glucose with methanol, silver carbonate, and the water liberated in the reaction as by-product,... 

In contrast to the result obtained with a-acetobromo-D-glucose, Isbell and Frush10 found the reaction of a-aeetobromo-D-mannose under parallel... 

Hurd and Holysz34 obtained a 20% yield of tetra-O-acetyl-jS-D-gluco-pyranosylbenzene (CVIII) on reacting a-acetobromo-D-glucose (CVII) with one mole of diphenylcadmium in boiling toluene and, under the same conditions, a 29% yield of tetra-O-acetyl-a-D-mannopyranosylbenzene (CX) was obtained from a-acetobromo-D-mannose (CIX). The authors... 

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