New oxidative tools for the functionalization of the cephalostatin north 1 hemisphere.
Org Lett
; 5(13): 2247-50, 2003 Jun 26.
Article
em En
| MEDLINE
| ID: mdl-12816420
ABSTRACT
Dimethyldioxirane (DMDO) C-H oxidation of ketone 17 to hemiketal 18 (82%), bis-dehydration to vinyl ether 21 (77%), and DMDO again provides C-23 axial alcohol 23 (99%). Routine processing, including a double-stereoselective Sharpless AD reaction (de >98%), gives alcohols 7 and 32. C-23 deoxy substrate 7 undergoes Suarez hypoiodite oxidative cyclization to (natural) beta spiroketal 34, but compound 32, bearing a C-23 silyl ether, generates unnatural spiroketal 33. [reaction see text]
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Ano de publicação:
2003
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Article