Jaime A. Rabi

Facile biomimetic synthesis of costunolide-1,10-epoxide, santamarin and reynosin

Abstract Reaction of costunolide with peracids yields costunolide-1,10-epoxide which undergoes ready cyclization to santamarin and reynosin.

The clemmensen reaction of tigogenin. A reinvestigation

Abstract The reaction of tigogenin ( 1b ) with amalgamated zinc yields tetrahydrotigogenin ( 2b ) and the furostan 3 . While 2b undergoes acid catalyzed elimination to give the rearranged product 7 , 3 spontaneously decomposes to a mixture of 4 and 5 .

Unambiguous transformation of eremanthin into (−)-estafiatin

Abstract A stereoselective synthesis of (−)-estafiatin ( 2a ) from eremanthin ( 1 ) has been achieved. The α configuration of the epoxide in the former is confirmed by chemical shift correlation with related oxides.

The reaction of eremanthin and isoeremanthin with bromine. Unprecedented simultaneous addition of Br2 to two isolated but topographically related double bonds.

The reaction of 1 with Br2 in CHCl3 proceeds with the simultaneous and stereospecific incorporation of two moles of Br2 to give 2 thus providing strong experimental evidence for the existence of Br3.