ABSTRACT
An efficient stereoselective total synthesis of (3R, 4S)-4-hydroxylasiodiplodin has been accomplished starting from known starting materials. The key steps involved in this synthesis are Stille cross coupling, alkylation of 1,3-dithiane and Yamaguchi macrolactonization.
Subject(s)
Heterocyclic Compounds, 2-Ring , Stereoisomerism , Alkylation , LactonesABSTRACT
The total synthesis of Benzannulated macrolide, (+)-Xestodecalactone A was accomplished starting from commercially available enantiomerically pure propylene oxide and 3,5-dihydroxyphenylacetic acid using Grignard reaction, alkylation of 1,3-dithiane and Yamaguchi macrolactonisation as key steps.
Subject(s)
Lactones , Macrolides , Stereoisomerism , AlkylationABSTRACT
The study describes the synthesis of new geminally disubstituted C-linked carbo-ß(2,2)-amino acids (ß(2,2)-Caas) with different carbohydrate side chains, and their use in the synthesis of ß(2,2)-peptides. The study infers that the side chain has an influence on the synthesis of peptides and their conformational behaviour.
Subject(s)
Amino Acids/chemical synthesis , Carbohydrates/chemistry , Peptides/chemical synthesis , Protein Folding , Protein Stability , Protein Structure, Secondary , StereoisomerismABSTRACT
C-linked carbo-ß(2)-amino acids (ß(2)-Caa), a new class of ß-amino acid with a carbohydrate side chain having d-xylo configuration, were prepared from d-glucose. The main idea behind the design of the new ß-amino acids was to move the steric strain of the bulky carbohydrate side chain from the Cß- to the Cα-carbon atom and to explore its influence on the folding propensities in peptides with alternating (R)- and (S)-ß(2)-Caas. The tetra- and hexapeptides derived were studied employing NMR (in CDCl(3)), CD, and molecular dynamics simulations. The ß(2)-peptides of the present study form left-handed 12/10- and 10/12-mixed helices independent of the order of the alternating chiral amino acids in the sequence and result in a new motif. These results differ from earlier findings on ß(3)-peptides of the same design, containing a carbohydrate side chain with d-xylo configuration, which form exclusively right-handed 12/10-mixed helices. Quantum chemical calculations employing ab initio MO theory suggest the side chain chirality as an important factor for the observed definite left- or right-handedness of the helices in the ß(2)- and ß(3)-peptides.
