Experiments directed towards the synthesis of anthracyclinones .28. Titanium(IV)- and tin(IV)-mediated cyclizations of ortho-methallyl-substituted homochiral dioxans

被引:8
作者
Cambie, RC [1 ]
Higgs, KC [1 ]
Rustenhoven, JJ [1 ]
Rutledge, PS [1 ]
机构
[1] UNIV AUCKLAND,DEPT CHEM,AUCKLAND,NEW ZEALAND
关键词
D O I
10.1071/CH9960677
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Metal chloride cyclizations of the 4-demethoxy anthraquinonyl 1',3'-dioxan (6) are highly diastereoselective, giving 9-chloro-9-methylanthracyclinones in high yield. The selectivity is inversely proportional to the strength of the Lewis acid, with the mild Lewis acid tin(IV) chloride/dimethylformamide affording an 82% yield of the diastereomer (21). The predominant products have a (7S) configuration and a trans relationship between the C7 side chain and the 9-chloro substituent. Cyclization of the analogous dimethoxy 1',3'-dioxan (4) with tin(IV) chloride/dimethylformamide is considerably less selective, but the major product also has a (7S)-trans stereochemistry. Titanium(IV) chloride effects stereorandom cyclization of (4).
引用
收藏
页码:677 / 688
页数:12
相关论文
共 17 条