Synthesis of new 1,2-dideoxy C-linked carbo-β-amino acids and α/β-peptides with 11/9-helix,helix-turn and helix-turn-helix structures

The present study describes the synthesis of new C-linked carbo-β-amino acids [β-Caa_(1,2-ddx)], with a 1,2-dideoxy D-xylo furanoside side chain (a tetrahydro furan derivative). The stereochemistry at the newly created amine centers was determined by modified Mosher method. The (S)-β-Caa_(1,2-ddx) prepared from d-mannose diacetonide were utilized for the synthesis of 1:1 α/β-peptides with L-Ala. The conformational analysis (NMR, MD and CD) revealed the presence of 11/9-helix, helix induced helix-turn (HT) and helix-turn-helix (HTH) in these peptides. These side chains with tetrahydrofuran ring facilitated the formation of robust helix, unlike some other side chains from earlier studies.     

Stereoselective Total Synthesis of Phenolic Nonadecanediol

A simple and highly efficient synthetic route has been developed for synthesis of 1‐(4‐hydroxyphenyl)nonadecane‐3,5‐diol ( 1 ). The two stereogenic centers were generated by employing proline asymmetric α‐hydroxylation (MacMillan α‐hydroxylation), Jacobsen's hydrolytic kinetic resolution (HKR), and, finally, Yamaguchi oxirane opening as key steps (Scheme 2).