Mercaptolysis

Reductive desulfurization with Raney nickel of the mercaptolysis products of streptomycin has supplied one of the keys to the elucidation of the structure and configuration of that antibiotic. Since the chemistry of streptomycin has recently been reviewed37 the reactions discussed here will be considered solely as examples of hydrogenolysis and their bearing upon the problem of the structure and configuration of streptomycin will be ignored. 

Kuehl, Flynn, Brink and Folkers38 in 1946 showed that mercaptolysis of streptomycin leads to the formation of an ethyl thiostreptobios-aminide diethyl thioacetal hydrochloride (XXX). The same substance... 

Zervas48 through the catalytic reduction of 2,3,4,6-tetraacetyl-2-hydroxy-D-glucal, has recently been prepared by the reductive desulfurization of ethyl tetraacetyl-l-thio-/ -D-mannopyranoside (XL),47 a substance which has been obtained through the mercaptolysis of mannosidostreptomycin48 and may be prepared through the prolonged action of ethyl mercaptan and hydrochloric acid on D-mannose. 

Y. Hama, H. Nakagawa, T. Sumi, X. Xia, and K. Yamaguchi, Anhydrous mercaptolysis of agar an efficient preparation of 3,6-anhydro-L-galactose diethyl dithioacetal, Carbohydr. Res., 318 (1999) 154-156. 

Although the penta-O-acetyl derivatives of /3-D-glucopyranose and /3-D-galactopyranose underwent rapid mercaptolysis at 0° in ethyl mercaptan (with zinc chloride as catalyst) to yield the corresponding ethyl tetra-0-acetyl-l-deoxy-l-thio-/3-D-glycopyranosides, the a-forms of these... 

Wolfrom and Thompson131 prepared ethyl tetra-0-acetyl-2-deoxy-2-thio-/3-D-fructopyranoside (CXVI) by mercaptolysis of the /3-pentaacetate (CXIV). Isbell6 has pointed out that, because of free rotation about the... 

Cl-to-C2 bond, the Cl-acetoxy group of ketose acetates can be expected to participate in replacement reactions at the anomeric center. The retention of configuration obtaining in the mercaptolysis of /3-D-fructopyranose pentaacetate (CXIV) suggests that the 1,2-cyclic ion (CXV) is an intermediate in the reaction. 

Fig. 2.—Relative Rates of Mercaptolysis of the Pentaacetates of D-Glucopyranose and D-Mannopyranose in Ethyl Mercaptan at 0° in the Presence of Zinc Chloride 105 1, /3-D-Glucopyranose Pentaacetate 2, S-D-Mannopyranose Pentaacetate 3, a-D-Mannopyranose Pentaacetate 4, a-D-Glucopyranose Pentaacetate.

Mercaptolysis of /3-D-glucopyranose pentaacetate in ethyl mercaptan at 0°, with zinc chloride as catalyst, gives ethyl tetra-O-acetyl-l-deoxy-1-thio-/S-D-glucopyranoside in 71% yield. Under the same conditions, a-D-glucopyranose pentaacetate reacted only very slowly, but it could be shown that the deoxy-thio-/3-D-glucoside is formed in much greater amount than is the a anomer. Mercaptolysis of the D-mannopyranose pentaacetates under the same conditions for 48 hours resulted in a 70% yield of ethyl tetra-O-acetyl-l-deoxy-l-thio-a-D-mannopyranoside from the /3-D-pentaacetate, and in a 60% yield from the a anomer.103 Inspection, by preparative paper chromatography, of the residual sirups, after deacetylation, led in each case to the isolation of the anomeric ethyl-1-... 

J. N. BeMiller, Agar. Preparation of agar and agarose methanolysis mercaptolysis, Methods, Carbohydr. Chem., 5 (1965) 65-69. 

C. Araki and S. Hirase, Chemical constitution of agar-agar. XV. Exhaustive mercaptolysis of agar-agar, Bull. Chem. Soc. Jpn., 26 (1953) 463 167 (Chem. Abstr., 49 (1955) 9516). 

D-Glucuronic acid215 and its 6,3-lactone216 combine readily with two equivalents of a thiol in the presence of hydrochloric acid (conditions of mercaptolysis) to give the dithioacetal (66) of the aldehydo form of the lactone. Compound 66 opens in sodium hydroxide216 or ammo-... 

The intervention of acid catalysis leads to irregular or third-order kinetics in several instances involving alcoholysis, aminolysis, or mercaptolysis (Table X, line 8). Small changes in the basicity of the substrate or of the amine produce large effects ... 

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