Trisubstituted (E)-Alkene Dipeptide Isosteres as β-Turn Promoters in the Gramicidin S Cyclodecapeptide Scaffold
摘要:
A concise synthesis of a gramicidin S analogue with trisubstituted (E)-alkene dipeptide isostere (TEADI) replacements at both D-Phe-Pro positions was realized. Conformational analysis demonstrated that TEADIs can serve as type II beta-turn promoters in a cyclic scaffold and successfully mimic a proline residue.
Trisubstituted (E)-Alkene Dipeptide Isosteres as β-Turn Promoters in the Gramicidin S Cyclodecapeptide Scaffold
摘要:
A concise synthesis of a gramicidin S analogue with trisubstituted (E)-alkene dipeptide isostere (TEADI) replacements at both D-Phe-Pro positions was realized. Conformational analysis demonstrated that TEADIs can serve as type II beta-turn promoters in a cyclic scaffold and successfully mimic a proline residue.
Enantioselective Addition of Bromonitromethane to Aliphatic <i>N</i>-Boc Aldimines Using a Homogeneous Bifunctional Chiral Organocatalyst
作者:Kenneth E. Schwieter、Jeffrey N. Johnston
DOI:10.1021/acscatal.5b01901
日期:2015.11.6
This report details the enantioselectivesynthesis of β-amino-α-bromo nitroalkanes with β-alkyl substituents, using homogeneous catalysis to prepare either antipode. Use of a bifunctionalBrønstedbase/acid catalyst allows equal access to either enantiomer of the products, enabling the use of Umpolung Amide Synthesis (UmAS) to prepare the corresponding L- or D-α-amino amide bearing alkyl side chains—overall
Phase Transfer Catalyzed Enantioselective Strecker Reactions of α-Amido Sulfones with Cyanohydrins
作者:Raquel P. Herrera、Valentina Sgarzani、Luca Bernardi、Francesco Fini、Daniel Pettersen、Alfredo Ricci
DOI:10.1021/jo061566u
日期:2006.12.1
A study into the use of a chiral phase-transfer catalyst in conjunction with acetone cyanohydrin to effect the enantioselective formation of α-amino nitriles from α-amido sulfones is described. This novel catalytic asymmetric Streckerreaction is analyzed with regard to the possible mechanistic basis.
The unprecedented use of phase-transfer catalysis (PTC) in an asymmetric hydrophosphonylation reaction allows the obtainment of a range of optically active α-amino phosphonic acid derivatives directly from α-amido sulfones.
A mild, efficient and highly regioselective addition of purine derivatives to N-Boc imines generated in situ in water was developed for the first time. A wide range of novel acyclic purine azanucleosides were synthesized in moderate to high yields through this transformation. This methodology was also appropriate for some other N-heterocycles.