New oxidative tools for the functionalization of the cephalostatin north 1 hemisphere.
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]
Lee
Jong Seok
JS
Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.
Fuchs
Philip L
PL
D003500:Cyclization; D004852:Epoxy Compounds / Q000737:chemistry; D004988:Ethers, Cyclic / Q000737:chemistry; D010084:Oxidation-Reduction; D010619:Phenazines / Q000737:chemistry*; D013141:Spiro Compounds / Q000737:chemistry*; D013237:Stereoisomerism
D004852:Epoxy Compounds; D004988:Ethers, Cyclic; D010619:Phenazines; D013141:Spiro Compounds; C064455:dimethyldioxirane