Enantiocontrolled synthesis of spirooxindoles based on the [5+2] cycloaddition of a Tp(CO)2Mo(pyridinyl) scaffold (Tp = hydridotrispyrazolylborate)

[GRAPHICS] A [5 + 2] cycloaddition of the pyridinyl pi -complex (-)-1 (98% ee) to methyleneoxindole 2 afforded the spirooxindole complex (-)-3 in high enantiomeric purity. Complex (-)-3 was converted to pyrrolidine (-)-8 (97% ee), which is related to potent cytotoxic analogues of the spirotryprostatins alkaloids.