Stereoselective Synthesis of .alpha.-Amino and .alpha.-Thio .beta.-Lactones by Conjugate Addition of Amine and Thiol Nucleophiles to .alpha.-Methylene .beta.-Lactones and Their Decarboxylation to Allylamines and Sulfides

Base-Catalyzed Hydroamination of Olefins: An Environmentally Friendly Route to Amines

“…In THF the cisdiastereoisomers (up to 77%) are formed as major products while in methanol high trans-diastereoselectivity (up to 93%) is observed. [52] Davies and Ichihara [53] reported the addition of (R)-amethylbenzylamine to methyl crotonate forming the corresponding (R,S)-b-amino derivative in good yield (35%, ethanol reflux), but with poor diastereoselectivity (< 4%). Addition of lithium amides derived from R-amethylbenzylamine to methyl crotonate gave the (R,R)-b-amino derivative but with no distinct stereoselectivity (yield 28%).…”

The Total Synthesis of ( - )-Tetrahydrolipstatin

“…[46] Identification of the diastereomers was facilitated by 1 H NMR analysis: β-lactone ring protons have characteristic coupling constants and the observed values of 6.1 and 3.9 Hz for cis-(3) and trans-(3) respectively were in agreement with literature values. [47] The control of regiochemistry in the key bromolactonization step was a pleasing result, as β,γ-unsaturated acids typically yield mixtures of βand γ-lactone regioisomers. [22,23] This high regioselectivity is thought to arise due to the influence of the inductively withdrawing C5 hydroxyl group, which disfavours substitution at the adjacent C4 position of the bromonium ion intermediate that leads to γ-lactone products.…”

Diastereoselective thiol conjugate addition on δ-alkylated-γ-silylated-α,β-unsaturated-δ-lactones

“…[8][9][10] Some of the studies, especially with the cysteine system are closely related to the investigation of the biological mechanism responsible for the carcinogenicity of lactones. 11 The thiol reagent often plays the role of solvent in thiol conjugate additions on δ-lactones in the presence of a basic amine.…”