Related Experiment Video
Updated: Jul 16, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Theoretical evidence for pyramidalized bicyclic serine enolates in highly diastereoselective alkylations
Carlos Aydillo1, Gonzalo Jiménez-Osés, Jesús H Busto
1Departamento de Química, Universidad de La Rioja, UA-CSIC, 26006 Logroño, Spain.
Abstract:
A new chiral serine equivalent and its enantiomer have been synthesized from (S)- and (R)-N-Boc-serine methyl esters (Boc: tert-butyloxycarbonyl). The use of these compounds as chiral building blocks has been demonstrated in the synthesis of alpha-alkyl alpha-amino acids by diastereoselective potassium enolate alkylation reactions and subsequent acid hydrolyses. Theoretical studies were performed to elucidate the stereochemical outcome of both the formation of five-membered cyclic N,O-acetals and the subsequent alkylation process, which occurs with total retention of configuration. This feature could be explained in terms of the high degree of pyramidalization of enolate intermediates.
Related Concept Videos
Stereochemical Effects of Enolization
α-Alkylation of Ketones via Enolate Ions
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Regioselective Formation of Enolates
Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.

