Acetates aldehydo

Similarly, compounds III and IV differ only in the acetate-aldehydo function at the end of the side chain. Again a two-electron transfer must occur with a second mole of LTA being required. 

In the case of the oximes of the aldose sugars, the situation is more complicated because of the possibility of both open-chain and cyclic structures. That aldose oximes can react in the open-chain form follows from the formation of the nitriles and from the isolation of acylated open-chain aldose oximes as secondary products in preparation of nitriles. For example, Wolfrom and Thompson, by the action of sodium acetate-acetic anhydride on n-glucose oxime, not only obtained pentaacetyl-D-glucononitrile, in 40% yield, but also isolated a small amount of hexaacetyl-oWeAydo-D-glucose oxime (V) identical with that prepared by mild acetylation of pentaacetyl-aWe%do-D-glucose oxime (IV) whose structure was assured by its formation from pentaacetyl-aldehydo-D-glucoae (III). 

Methylation of carbazole phenolic oxygen has been achieved using dimethyl sulfate without reaction at nitrogen. Demethylation of carbazole methyl ethers has been achieved with hydrobromic acid-acetic acid, boron trichloride,and pyridine hydrochloride. Selective demethylation of methoxyl ortho to an aldehydo function has been achieved using boron trifluoride. ° ° Partial demethylation of 1-methoxy-3-formylcarbazole occurred during Wolff-Kischner reduction." ... 

Periodate oxidation of 2-acetamido-1,2-dideoxy-3,4-0-isopropylidene-D-glucitol (33) affords 4-acetamido-4,5-dideoxy-2,3-0-isopropylidene-aldehydo-c-xylose, which, on hydrolysis with acetic acid, gives31 the pyrrolidine 34. The same series of reactions was performed31" on the... 

M. Kiso, A. Yasm, and A. Hasegawa, Synthesis of 2-azido-2-deoxy-3,4 5,6-di-0-isopropyl-idene-aldehydo-D-aanoose dimethyl acetal and 4-azido-4-deoxy-2r3 5,6-di-0-isopropyI-i ene-aldehydo-D-piictoee dimethyl acetal, Carbohydr. Res. 127 137 (1984). 

Closely similar results were obtained with various diphenyl dithioacetal acetates (7), with the unsubstituted diethyl dithioacetals (8), and with the aldehydo-pentose peracetates (9) and the tetra-O-acetylaldo-pentose dimethyl acetals (10). Subsequent work in other laboratories has shown the same general principles for the methyl 5-hexulosonates (11) and the pentononitrile tetraacetates (12), two examples where a full series of stereoisomers has been studied. Other workers have investigated isolated examples or partial series (13, 14, 15, 16, 17, 18), and parallel work by x-ray crystallography (19, 20, 21, 22) on acyclic sugar derivatives in the solid state has shown excellent correlation with the general principles outlined here for the molecules in solution. 

Fully acetylated aldonic acids can be prepared by oxidation of aldehydo-sugar peracetates. Direct acetylation of certain aldonic acid salts is possible, and addition of cadmium salts, in particular, affords high yields of acetates. The synthesis can also be accomplished by deamination of the readily prepared, acetylated amides with nitrous acid or nitrosyl chloride. Examples of the various methods are given in Ref. 86. 

In perchloric acid, hexoses and pentoses are oxidized by Ce(IV) via formation of two complex intermediates. The first is partly oxidized following Michaelis-Menten kinetics and partly dissociated to the second, which is oxidized more slowly than the former.180 The first step in the oxidation of aldoses by Tl(III) in the same medium involves the C-l-C-2 cleavage of the aldehydo form of the sugar. Thus, D-glucose gives D-arabinose and formic acid. With an excess of oxidant the final product is carbon dioxide.181 In the presence of a catalytic amount of sulfuric acid in acetic acid, Tl(III) oxidizes maltose and lactose to the corresponding disaccharide aldonic acids. The reaction showed activation enthalpies and enthropies characteristic of second-order reactions.182... 

A series of C-glycosylated ethylenes have been prepared by several workers10,31-35 for different purposes, mainly for the subsequent synthesis ofbranched-chain nucleosides. Lange and Szarek reported31 an attempted synthesis of 5,6-dideoxy-l,2-0-isopropylidene-a-D-xyZo-hex-5-enofuranose (15a) and its acetate (15b) from the aldehydo... 

---