Enantioselective Formal Synthesis of the Cytotoxic Topoisomerase
II Inhibitor Deoxythysanone, Catalyzed by Chiral Spiroborate Ester
摘要:
Bioactive pyranonaphthoquinone analogs, (1R,3S)-deoxythysanone, (1R,3S)-thysanone, and (1R,3S)-demethoxythysanone can be efficiently synthesized from a common intermediate product, (S)-3-methyl-3,4-dihydro-1H-isochromene-5,8-dione. We have developed a short synthetic route to pyranonaphthoquinone antibiotics, which involves enantioselective reduction of homobenzylic ketone in the presence of a chiral spiroborate catalyst with 87% enantiomeric excess as the key step. The subsequent oxa-Pectet-Spengler reaction, followed by oxidative demethylation, afforded deoxythysanone.
DDQ-induced and stereoselective functionalization at heterosubstituted benzylic positions by carbon nucleophiles
作者:Xu Yao-Chang、Caroline Roy、Elaine Lebeau
DOI:10.1016/s0040-4039(00)61387-4
日期:1993.12
DDQ-Induced, Anomeric Specific, and Diastereoselective Benzylic Glycosidation: A Novel Approach to Heterocyclic Anthracycline Antibiotics
作者:Yao-Chang Xu、Elaine Lebeau、Giorgio Attardo、Peter L. Myers、John W. Gillard
DOI:10.1021/jo00096a032
日期:1994.8
A novel and efficient method for the oxidative glycosidation at the heterosubstituted benzylic positions with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) is described. The reaction is stereospecific with 3-substituted isochromans and isothiochroman, as well as diastereoselective with non-3-substituted isochromans. The glycosidation with a mixture of alpha- and beta-anomeric free sugars gives alpha-glycosides with absolute stereochemical control on the anomeric center. The synthetic utility of this novel methodology is demonstrated by a short, efficient, and stereoselective total synthesis of heteroanthracycline antitumor reagents.