Aspects of the tautomerism of 2-(d-galacto-1,2,3,4,5-pentahydroxypentyl)benzothiazoline |
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Authors: | Regina Blattner Robert J Ferrier Peter C Tyler |
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Institution: | Department of Chemistry, Victoria University of Wellington, Wellington New Zealand |
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Abstract: | The benzothiazoline (1, R1 = R2 = H) formed by the reaction of d-galactose with o-aminobenzenethiol gives biso-(α-d-galactofuranosylamino)benzenethiol]-mercury(II) (2, R = H) on treatment with mercury(II) acetate in refluxing acetic acid. O-Acetylation of the chelate occurs smoothly, and demercuration of the product with hydrogen sulphide gives the thiol (3, R1 - Ac, R2 = R3 = H) which, with catalytic acid or when kept in chloroform solution, isomerises to the thiazoline compound (1, R1 = Ac, R2 = H). Under mild acetylating conditions, this product (and the starting material) gives diastereoisomeric 2,3,4,5,6-penta-acetates (1, R1 = R2 = Ac), but appreciable reversion to thiol occurs with acyl chlorides, with the consequence that thioesters (3, R1 = R2 = Ac, R3 = H; R1 = Ac, R2 = Bz, R3 = H) were major products. The value of the tetraester (1, R1 = Ac; R2 = H) as a means of obtaining galactose derivatives specifically modified at C-4 is therefore limited. |
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