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Synthesis 1999; 1999(2): 317-325
DOI: 10.1055/s-1999-3384
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Highly Functionalised Cyclopentanes by Radical Cyclisation of Unsaturated Bromolactones III. Preparation of Carbaaldohexofuranoses. Determination of the Relative Configuration at C-4/C-5 of 2,3-Unsaturated Heptono-1,4-lactones by Means of 1H NMR Spectroscopy

Anne Marie Horneman* , Inge Lundt
  • *Department of Organic Chemistry, Technical University of Denmark, Building 201, DK-2800 Lyngby, Denmark; Fax +45(45 93)39 68; E-mail: okil@pop.dtu.dk
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Publication Date:
31 December 1999 (online)

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Two new carbaaldohexofuranoses, carba-β-d-glucofuranose and carba-α-l-mannofuranose, have been prepared using 5,6-O-isopropylidene-d-glycero-l-galacto-heptono-1,4-lactone (6) as the starting material. The key step was a highly stereoselective intramolecular 5-exo-trig radical cyclisation of C-2 substituted 2,3-unsaturated 7-bromo-7-deoxyheptono-1,4-lactones promoted by tributyltin hydride. Assignment of the configuration of the unsaturated lactones was based upon NMR data of related compounds. The starting material, compound 6, was obtained by chain elongation of d-gulose, and a facile method for separation of the epimers from the chain elongation has been developed. Thus 5,6-O-isopropylidene-d-glycero-l-galacto-heptono-1,4-lactone (6) and d -glycero-l-talo-heptono-1,4-lactone (5) were isolated crystalline in ca. 30% and 10% yield, respectively.

carbasugars - radical cyclisation - bromoaldonolactones - 2,3-unsaturated 1,4-aldonolactones - heptonolactones