The reactivity of the title compounds with different nucleophiles has been checked and it was shown that products from reaction with sodium phenylthiolate result from an elimination-addition process in which protoanemonin is the key intermediate. The synthesis of (−)-(R)-β-angelica lactone is reported for the first time.
Conjugate addition of potassiumtrifluoro(organo)borates 2 to dehydroalanine derivatives 1, mediated by a chiral rhodium catalyst and in situ enantioselective protonation, afforded straightforward access to a variety of protected alpha-amino esters 3 with high yields and enantiomeric excesses up to 95%. Among the tested chiral ligands and proton sources, Binap, in combination with guaiacol (2-methoxyphenol)
Further support to the hypothesis that antimutagenic activities of α, β-unsaturated carbonyl compounds against UV-induced mutagenesis of E. coli may be due to an interaction with thiol groups were obtained by an experiment with the supplement of glatathione to the assay medium. Antimutagenic activity against MNNG induced mutation was also observed.
A short synthesis of the title compound, 16, from d-ribonolactone is described. Two alternative approaches differing in the timing of the CC double bond creation are used to prepare some chiral derivatives of 16. (−)-Ranunculin, a glycoside present in Ranunculaceae, has been synthesized for the first time.
Synthetic approaches to either homochiral or achiral derivatives of 3-hydroxy-2(5H)-furanone (isotetronic acid)
作者:Joaquim Bigorra、Josep Font、Cristina Ochoa de Echagüen、Rosa M. Ortuño
DOI:10.1016/s0040-4020(01)81841-x
日期:1993.7
Several title compounds were synthesized according to new methods based either on the use of D-ribonolactone as a chiral precursor or on the cyclization of 2,4-dioxopentanoic acid as a suitable achiral precursor. Base-induced elimination and subsequent acid-promoted ring contraction is an efficient protocol for the preparation of isotetronic acids from 2-O-alkyl-3,4-O-benzylidene-D-ribono-1,5-lactone derivatives