Asymmetric synthesis of (1R,8S)- and (1S,8S)-1-hydroxypyrrolizidin-3-ones from Boc-L-prolinal and (S)- and (R)-[(η<sup>5</sup>-C<inf>5</inf>H <inf>5</inf>)Fe(CO)(PPh<inf>3</inf>)(Ac)], respectively
Beckett RP., Davies SG.
The aldol reaction between the aluminium enolate derived from (S)-[(η<sup>5</sup>-C<inf>5</inf>H<inf>5</inf>)Fe(CO)(PPh<inf>3</inf>)(Ac)] (S)-(3) and Boc-L-prolinal (S)-(2) gives, after deprotection and decomplexation, (1R,8S)-1-hydroxypyrrolizidin-3-one, (1), while its epimer (1S,8S)-(1) is obtained in a similar way from (R)-(3), the inherent stereocontrol of (2) being overpowered by the iron chiral auxiliary.