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]

[1]  P. Fuchs,et al.  Dyotropic rearrangement facilitated proximal functionalization and oxidative removal of angular methyl groups: efficient syntheses of 23'-deoxy cephalostatin 1 analogues. , 2002, Journal of the American Chemical Society.

[2]  T. Prangé,et al.  A convenient synthesis of C-22 and C-25 stereoisomers of cephalostatin north 1 side chain from spirostan sapogenins. , 2002, Organic letters.

[3]  P. Fuchs,et al.  The first total synthesis of (corrected) ritterazine M. , 2002, Organic letters.

[4]  M. Boyd,et al.  Outer-ring stereochemical modulation of cytotoxicity in cephalostatins. , 2000, Organic letters.

[5]  M. Boyd,et al.  On topography and functionality in the B-D rings of cephalostatin cytotoxins. , 1999, Bioorganic & medicinal chemistry letters.

[6]  Lontsi,et al.  Fontaineine, a new alkaloid from fontainea pancheri , 1998, Journal of natural products.

[7]  P. Fuchs,et al.  Interphylal Product Splicing: The First Total Syntheses of Cephalostatin 1, the North Hemisphere of Ritterazine G, and the Highly Active Hybrid Analogue, Ritterostatin GN1N1 , 1998 .

[8]  S. Matsunaga,et al.  Isolation of 13 New Ritterazines from the Tunicate Ritterella tokioka and Chemical Transformation of Ritterazine B(1). , 1997, The Journal of organic chemistry.

[9]  P. Fuchs,et al.  Chromium [II]-mediated reductive cleavage of a tertiary halide bearing three β-alkoxy groups. Synthesis of the north hexacyclic steroid unit of the cephalostatin family , 1995 .

[10]  P. Fuchs,et al.  Synthesis of the South hexacyclic sterold unit of cephalostatin 7 , 1995 .

[11]  Stephen C. Smith,et al.  Synthesis and Biological Activity Of Unsymmetrical Bis-Steroidal Pyrazines Related to the Cytotoxic Marine Natural Product Cephalostatin 1 , 1994 .

[12]  David J. Williams,et al.  A highly convergent total synthesis of the spiroacetal macrolide (+)-milbemycinβ1 , 1989 .