CYCLIZATION REACTIONS OF TETHERED RADICALS DERIVED FROM 4-O-SUBSTITUTED ALPHA-D-ERYTHRO-OCTA-2,6-DIENOPYRANOSIDES - STEREOSELECTIVE ACCESS TO CARBOCYCLES AND BRANCHED-CHAIN SUGARS

被引:14
作者
LOPEZ, JC [1 ]
GOMEZ, AM [1 ]
FRASERREID, B [1 ]
机构
[1] DUKE UNIV,DEPT CHEM,PAUL M GROSS CHEM LAB,DURHAM,NC 27708
关键词
D O I
10.1071/CH9950333
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The chemo- and stereo-selectivities in the cyclization of tethered radicals, derived from alpha-D-erythro-octa-2,6-dienopyranosides, in which there is competition between 5-exo and 6-exo ring closures, have been examined. Use of silicon tethers resulted in a preferred 6-exo-trig addition. However, tethered mixed iodo acetals have shown an unprecedented relation between the stereogenic centre in the acetal and the preferred addition pathway. In addition, changes in the oxidation state at the termini of the olefins have a profound effect upon site selectivity, thus leading to 3-deoxy 3-C-substituted carbohydrates, off-template branched-chain sugars, or functionalized cyclopentanes.
引用
收藏
页码:333 / 352
页数:20
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