Synthesis of 1,2,4-Oxadiazole-, 1,3,4-Oxadiazole-, and 1,2,4-Triazole-Derived Dipeptidomimetics
摘要:
Three series of heterocyclic dipeptidomimetics have been synthesized. The compounds were designed as amino acid-glycine mimetics containing 1,2,4-oxadiazole, 1,3,4-oxadiazole, and 1,2,4-triazole ring systems, useful as building blocks in the synthesis of modified peptides. The heterocyclic moieties were chosen according to their geometrical, electrostatical, and hydrogen bonding properties together with the synthetic accessibility. The syntheses started with Boc-protected L-amino acids (Ala, Gly, Asp, Phe, Ser, Arg, Cys, and Pro), and the reaction conditions were chosen to allow for the formation of products with high enantiopurity. The enantiomeric excess was determined by HPLC using chiral stationary phases.
Diastereoselective Alkylations of a Protected Cysteinesulfenate
摘要:
To further understand stereoselection in the alkylation of sulfenate anions, a protected cysteinesulfenate was generated in THF solution at low temperature. Introduction of a reactive alkylating agent brings about a cysteinyl sulfoxide in 51-75% yield, with diastereomeric ratios at the sulfinyl group ranging from 83:17 to 95:5. An internally complexed lithium counterion is proposed to account for the stereoselectivity.
planetary ball mill proved to be more suitable for the synthesis of aminoesters from N-protected aminoacids via a one-pot activation/esterification reaction in the presence of various dialkyl dicarbonates or chloroformates. The spot-to-spot reactions were straightforward, leading to the final products in reduced reaction times with improved yields and simplified work-up procedures.