Characterization and interconversions of 2-S-ethyl-2-thio-D-mannose diethyl dithioacetal and the facile epimerization of 2-thio-D-mannopyranose derivatives

Carbohydr Res. 1996 Mar 22;283:53-7. doi: 10.1016/0008-6215(95)00399-1.

Abstract

3,4,5,6-Tetra-O-benzoyl-D-glucose diethyl dithioacetal (2) reacts with ethanethiol under acidic conditions to afford 3,4,5,6-tetra-O-benzoyl-2-S-ethyl-2-thio-D-mannose (3), the stereochemistry at C-2 of which has been assigned by chemical conversions on its debenzoylated derivative, the crystalline 2-S-ethyl-2-thio-D-mannose diethyl dithioacetal (4). In the presence of mercuric chloride (1.1 molar equiv), 4 is converted into crystalline ethyl 2-S-ethyl-1,2-dithio-alpha-D-mannofuranoside (5). Complete demercaptalation of 4 affords syrup 2-S-ethyl-2-thio-D-mannopyranose (6), which was characterized as its phenylhydrazone 7 and the crystalline alpha-pyranose tetraacetate 9. Extended treatment of 4 with mercuric chloride and aqueous sodium hydrogencarbonate resulted in isolation of 6, along with its crystalline 2-epimer, 2-S-ethyl-2-thio-beta-D-glucopyranose (10). Remercaptalation of 6 affords the manno diethyl dithioacetal 4 as the major product, whereas similar treatment of 10 yields ethyl 2-S-ethyl-1,2-dithio-alpha-D-glucopyranoside (13). The mechanism of conversion of 2 into 3, as well as the unusually facile interconversion of 2-S-ethyl-2-thio-D-mannose (6) and its D-gluco epimer 10, has been investigated.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetals / chemical synthesis
  • Acetals / chemistry
  • Carbohydrate Conformation
  • Glucose / analogs & derivatives
  • Magnetic Resonance Spectroscopy
  • Mannose / analogs & derivatives*
  • Molecular Conformation
  • Molecular Structure
  • Sulfides / chemical synthesis
  • Sulfides / chemistry*

Substances

  • Acetals
  • Sulfides
  • Glucose
  • Mannose