期刊
TETRAHEDRON
卷 56, 期 24, 页码 3995-4000出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S0040-4020(00)00299-4
关键词
carbohydrate; selenium; free-radical; samarium iodide; ring closure
2,3,4-Tri-O-benzyl-1,5-dideoxy-5-seleno-D-pentopyranose sugars (16, 23, 24) are readily prepared by thermolysis of 2,3,4-tri-O-benzyl-5 -benzylseleno-D-ribit-1-yl formate, 2,3,4-tri-O-benzyl-5-benzylseleno-D-xylit-1-yl formate and 2,3,4-tri-O-benzyl-5-benzylseleno-D-arabit-1-yl formate (13, 21, 22) in transformations which involve intramolecular nucleophilic attack of the benzylseleno moiety with concomitant loss of carbon dioxide and phenylselenoate. In a complementary procedure, treatment of 2,3,4-tri-O-benzyl-5-benzylseleno-5-deoxyribose (19) with samarium(II) iodide in THF affords 2,3,4-tri-O-benzyl-5-deoxy-5-seleno-D-ribopyranose (26) in 50% isolated yield in a process Most likely involving intramolecular homolytic substitution at the selenium atom in the selenosugar. (C) 2000 Elsevier Science Ltd. All rights reserved.
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