Reaction of 3 with lithium tributylstannane occurs with high levels of diastereoselectivity
, such that only one isomer of 4 is observed.
These findings support the assumption that the structure of the substrate is the most important factor in the control of reaction diastereoselectivity
The study of stereoselectivity has evolved from issues of diastereoselectivity
, through auxiliary-based methods for the synthesis of enantiomerically pure compounds (diastereoselectivity
followed by separation and auxiliary cleavage), to asymmetric catalysis.
The reactions proceed in high yields with near complete diastereoselectivity
As the ratio of 4a : 4b does not depend much on the oxidant, it is very likely that the diastereoselectivity of the oxidation is controlled by the substrate.
The diastereoselectivity of hydroxylation was found to be mainly substrate-dependent.
Increasing the reactivity of the other component (dienophile 3) by introduction of a nitro group did the trick, and the Diels Alder cycloadduct was obtained in 60% yield with 72% diastereoselectivity
was accomplished for a key intermediate in the synthesis of carbapenem antibiotics using (R,R)-2,4-bis(diphenylphosphine)pentane as the chiral ligand.
Normant discussed his highly diastereoselectivity use of bisorganometallic reagents such as allyl vinyl zinc species to provide coupled products of predictable stereochemistry.
These synthons undergo a number of transformations such as Diels-Alder cyclizations and Michael additions with high diastereoselectivity providing useful entries to |beta~-aminoacids, |beta~-lactams and natural products such as lignans.
Recent work has centered on studying the stereoselectivity of reactions of certain [beta]-ketosulfones, in which the proximity of a sterically hindered sulfonyl group to other functional groups leads to diastereoselectivity
in the reaction of nucleophiles with the carbonyl group.