Altropyranoside chloride

Many other glycosides have been subjected to selective chlorination with sulfuryl chloride. Methyl /3-L-arabinopyranoside afforded methyl 4-chloro-4-deoxy-a-D-xylopyranoside 2,3-di(chlorosulfate) in 29% yield, whereas the a-L anomer gave357 methyl 3,4-dichloro-3,4-dideoxy-/3-i)-ribopyranoside 2-(chlorosulfate) (30%). Methyl /3-d-ribopyranoside was converted into methyl 3,4-dichloro-3,4-dideoxy-a-L-arabinopyranoside through the action of pyridine hydrochloride on its 2,3,4-tri(chlorosulfate).358 Methyl a-D-lyxopyranoside gave only the 2,3,4-tri(chlorosulfate),353 as would be expected from the disposition of its hydroxyl groups, similar to that in the rhamno- and manno-pyranosides. Methyl a-D-altropyranoside was transformed into the 6-chloro-6-deoxy 2,3,4-tri(chlorosulfate) derivative in 80% yield.353... 

The reaction of 39 with methyl 4,6-0-benzylidene-2-deoxy-2-iodo-a-D-altropyranoside (48) gave a complex mixture of products, from which methyl 4,6-0-benzylidene-2,3-dideoxy-a-D-eryf/iro-hex-2-eno-pyranoside (50) could be isolated. The formation of 50 was ex-plained83(b) by attack by chloride ion on the iodine atom in intermediate 49, followed by elimination of the substituent at C-3. Compound 50 itself reacts with reagent 39, and, therefore, prolonged reaction times led to extensive decomposition. 

A novel method of opening of oxiranes involves the use of (chlo-romethylene)dimethyliminium chloride (39) [see Section II,2c p. 250], monochlorodeoxy or dichlorodideoxy derivatives are obtained, depending upon the reaction conditions employed.83 Thus, methyl 2,3-anhydro-4,6-0-benzylidene-a-D-allopyranoside (110) reacts with 39 in 1,1,2,2-tetrachloroethane at room temperature to give, upon hydrolysis of the primary adduct 111 with an aqueous solution of sodium hydrogen carbonate, methyl 4,6-0-benzylidene-2-chloro-2-deoxy-3-0-formyl-a-D-altropyranoside (112). If a solution of 39 and 110 in 1,1,2,2-tetrachloroethane is heated at reflux temperature, methyl 3,4-0-benzylidene-2,6-dichloro-2,6-dideoxy-o -D-altropyrano-side (113) is obtained in high yield the n.m.r. spectrum of 113, like that of 47 (see Section II, 2c p. 250), showed the presence of two diastereoisomers which differed in the configuration of the benzyl-idene-acetal carbon atom. 

Neighboring-group participation by the vicinal, trans-acetoxyl group (see p. 125) serves to explain the abnormal behavior of methyl 4-0-acetyl-2,3-anhydro-6-0-benzyl- or -trityl-a-D-gulopyranoside with hydrogen chloride in acetone, or with 80% aqueous acetic acid, which give D-galactose, instead of the D-idose, derivatives.67 In the same way, 2-0-acetyl-3,4-anhydro-D-altropyranosides yield D-man-nosides, not D-idosides.9 6z(see p. 125). 

The reaction of sucrose 2,3-manno-epoxide with potassium thioacetate and ammonium chloride in aqueous ethanol gave the expected 3-5>-acetyl-3-thio-altropyranoside (101). Treatment of 6,6,-dibromo-6,6,-dideoxysucrose hexaacetate with potassium thioacetate and A/, Ak dimethyl thiocarbamate gave the corresponding derivatives of 6,6,-dithiosucrose. The air oxidation of 6,6,-dithiolsucrose gave the bridged 6,6,-episulfide. A detailed conformational study of sucrose 6,6,-dithiol and sucrose 6,6 -episulfide revealed that they are similar but distinguishable (102). 

Treatment of 1,2 5,6-di-O-isopropylidene-a-D-allofuranose with methanolic hydrogen chloride for 20 hours affords the methyl 2,3-0-isopropylidene- and 2,3 5,6-di-0-isopropylidene-/3-D-allofurano-sides 118 again, migration to a favorably disposed hydroxyl group occurs. Evans62 reported the rearrangement of methyl 4,6-0-iso-propylidene-a-D-altropyranoside to the 3,4-acetal in acetone-sulfuric acid. 

It should be emphasized that, in order to make an assessment of the stereochemical principles involved in the formation of cyclic acetals of aldoses and aldosides, the reaction products from a given condensation must be analyzed quantitatively, and the structures of the products determined. In addition, the reaction should, ideally, have reached equilibrium under truly reversible conditions. It now seems that the interpretation of some of the previous results must be carefully reconsidered. The valuable investigations of Buchanan and Saunders have revealed the possibility that condensations catalyzed by zinc chloride may not proceed in a truly reversible manner. Dorcheus and Williams also remarked that the catalytic action of zinc chloride will be lost through formation of the hydrated complex, ZnCU (H80)2. This change will result in kinetic control of the reaction. It has been found, for example, that reaction of methyl a-D-altropyranoside (13) with acetone and sulfuric acid affords a 42% yield of the 3,4-0-isopropylidene acetal. Using zinc chloride as the catalyst, both the 3,4- and the 4,6-0-isopropylidene acetal are obtained. Similar results were re-... 

Amino acid 88 obtained from methyl 3-deoxy-3-amino-altropyranoside 87 was treated with methanesulfonyl chloride in the presence of sodium bicarbonate and gave the /3-lactam 89. Compound 89 was subsequently subjected to ring-opening polymerization to afford optically active polyamide 90... 

Syntheses of naturally occurring (-f)-blastmycinone (280) and its C-3 and C-4 stereoisomers have been reported. The C-butyl branch was introduced by reaction of methyl 2,3-anhydro-4,6-0-benzylidene-a-D-mannopyranoside with n-butyl magnesium chloride to give methyl 4,6-6>-benzylidene-3-C-butyl-3-deoxy-a-D-altropyranoside, which was degraded and transformed into the i. arabino isomer (280) (see Vol. 9, p. 204). 

Methyl 4,6-0-benzylidene-2-deoxy-a-D-altropyranoside refluxed 20 min. with p-toluenesulfonyl chloride in pyridine methyl 4,6-0-benzylidene-a-D-erz/fhro-hex-2-enopyranoside. Y 95%. F. e. with methanesulfonyl chloride s. R. U. Le-mieux, E. Fraga, and K. A. Watanabe, Gan. J. Ghem. 46, 61 (1968). 

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