Herstellung von steroisomeren 3-Sulfinylbuttersäuren aus (<i>R</i>)- und (<i>S</i>)-4-Methyl-2-oxetanon
作者:Richard Breitschuh、Dieter Seebach
DOI:10.1055/s-1992-34181
日期:——
The β-lactone ((S) and (R)-4-methyl-2-oxetanone,1 , ent-1), readily available from (R)- and (S)-3-hydroxybutyric acid, is opened by sodium hydrosulfide, sodium alkane- and arenethiolates, respectively, with inversion of configuration. The resulting 3-(alkylthio)-2f, 2g, and 3-(arylthio)butyric acids, 2b-2e, ent-2h-2k (Table 1), oxidized with hydrogen peroxide in acetone to give the corresponding 3-(alkylsulfinyl)- and 3-(arylsulfinyl)butyric acids as mixtures of diastereoisomers3b-3k and 4b-4k. These are separated and the purelike and unlike diastereoisomers isolated and fully characterized (Table 4). Configurational assignments rest upon a crystal structure analysis (Figure 1) and comparison of properties in the two series.
An asymmetric thia-Michael addition of arylthiols to α,β-unsaturated carboxylic acids using a thiourea catalyst that bears arylboronic acid and tertiary amine moieties is reported. Both enantiomers of the Michael adducts can be obtained in high enantioselectivity and good yield merely by changing the solvent. The origin of the chiralityswitch in the products was examined in each solvent via spectroscopic