Overman: Possible [3, 3] rearrangement 2: 1 mixture of epimers Two possible mechanisms explain the formation of the minor diastereomer: 得年”,一改 Overman: Spiroannulations 人 1.5: 1 mixture Tetrahedron, 1997. 53. 8927 32C-073/189910:27PMOverman: Possible [3,3] rearrangement JACS, 1991, 113, 5365 Ph OH OH O H Ph O O Ph Ph 2:1 mixture of epimers O OH Ph Ph + O Ph OH + or O Ph HO Ph + O O Ph Ph Ph O Ph OH + Ph O Ph H OH [3,3] Two possible mechanisms explain the formation of the minor diastereomer: Overman: Spiroannulations Tetrahedron, 1997, 53, 8927 OTMS XR + XR OTMS + b a O O XR XR Prins OTMS OMe OMe TMSOTf, DTBMP CH2Cl2, rt, 82% O RuCl3•3H2O NaIO4, CCl4 MeCN, H2O 68-88% O O bond a bond b 1.5:1 mixture DTBMP = 2,6-t-butyl-4-methylpyridine OMe 32C-07 3/18/99 10:27 PM