Diastereocontrol of nucleophilic attack of the rubanone carbonyl group via remote siloxy tether. Establishing the natural configuration at carbon C-3 of cinchona alkaloid

Article abstract of DOI:10.1016/S0040-4020(97)00609-1

Cinchona alkaloid derivatives with natural configuration at C-3 have been constructed by Grignard reaction of protected rubanone 1-TBDS. The organomagnesium reagent attacks preferentially from the sterically more hindered endo face. Even L-Selectride reacts endo-selectively (9 : 1).