Synthesis of Enantiopure 3-Quinuclidinone Analogues with Three Stereogenic Centers:  (1S,2R,4S)- and (1S,2S,4S)-2-(Hydroxymethyl)-1-azabicyclo[2.2.2]octan-5-one and Stereocontrol of Nucleophilic Addition to the Carbonyl Group

The pseudoenantiomeric title compounds have been prepared from quincorine (QCI) and quincoridine (QCD), respectively, in enantiopure form following an efficient six-step pathway. Nucleophilic attack at the carbonyl group proceeds preferentially from the supposedly more hindered endo π-face, giving quinuclidinols with natural configuration at C5 (up to 97%). π-Face selectivity is highest in the QCD series with bulky O-protecting groups, involving an unprecedented 1,7-stereoinduction.