A short stereocontrolled synthesis of hydroxyethylene dipeptide isosteres
摘要:
A stereocontrolled synthesis of protected hydroxyethylene dipeptide isosteres 14 and 16 is described. It provides the 2R,4S,5S epimers required for the preparation of aspartic proteinase inhibitors. The choice of a benzene ring as a precursor to the carboxylic acid function has enabled us to use the readily accessible chiral Grignard reagent 3 which reacts with the protected alpha-amino aldehyde 8 stereoselectively. Kilogram quantities of 16 have been produced by this route in a satisfactory overall yield. The combination of N- and 0-protecting groups employed facilitates the incorporation of 14 or 16 into peptide-based enzyme inhibitors.
A new class of chiralruthenium catalysts is introduced in which ruthenium is cyclometalated by two 7-methyl-1,7-phenanthrolinium heterocycles, resulting in chelating pyridylidene remote N-heterocycliccarbene ligands (rNHCs). The overall chirality results from a stereogenic metal center featuring either a Λ or Δ absolute configuration. This work features the importance of the relative metal-centered
or M) in the corresponding hydrogen-bondedassemblies 1(3).(CA)(6) (de>98 %). The high degree of chiral induction results from the presence of six chiral centers in close proximity (C(alpha)) to the core of the assembly. A much lower level of chiral induction is observed for assemblies with chiral centers that are more remote (C(beta)). All diastereomerically pure assemblies 1(3).(CA)(6) exhibit very
杯[4]芳烃1的二蜜胺组分中或氰尿酸酯组分CA中存在的手性中心在相应的氢键键合组件1(3)。(CA)(6)(de)中定量诱导一种惯性(P或M)。 > 98%)。高度的手性诱导是由于六个手性中心(Cα)与装配体的核心非常接近。对于具有更远的手性中心(Cβ)的装配体,观察到了更低的手性诱导水平。所有非对映体纯组装1(3)。(CA)(6)都显示出非常高的CD活性(deltavarepsilon(max)约100 L mol(-1)cm(-1)),与低CD活性(deltavarepsilon (最大)
Chirality and Fragrance Chemistry: Stereoisomers of the Commercial Chiral Odorants Muguesia and Pamplefleur
作者:Agnese Abate、Elisabetta Brenna、Claudio Fuganti、Francesco G. Gatti、Tommaso Giovenzana、Luciana Malpezzi、Stefano Serra
DOI:10.1021/jo048445j
日期:2005.2.1
The work describes the enzyme-mediatedpreparation and the odor evaluation of the single stereoisomers of the commercial odorants Muguesia and Pamplefleur. The synthetic approach to Muguesia stereoisomers helped to clear the assignment of the relative configuration of intermediate diols 5. The odor response of Pamplefleur isomers was found to be rather unusual. No stereoisomer prevailed, but each one
It is intended to provide antipruritics (drugs to control itching, antiitch agents and drugs to stop itching). It is found out that a compound having an agonistic activity to the cannabinoid receptor shows an antipruritics effect.