Value of zeolites in asymmetric induction during photocyclization of pyridones, cyclohexadienones and naphthalenones
作者:Karthikeyan Sivasubramanian、Lakshmi S. Kaanumalle、Sundararajan Uppili、V. Ramamurthy
DOI:10.1039/b702572f
日期:——
approaches, have been examined within zeolites with the aim of achieving asymmetricinduction during the photocyclization of cyclohexadienone, naphthalenone and pyridone derivatives. Within zeolites, enantioselectivity as high as 55% and diastereoselectivity as high as 88% have been obtained. The observed stereoselectivities are significant given the fact that these reactions gave very little stereoselectivities
vinylboronates and α‐iminoamides are effectively catalyzed by the novel hydroxy–thiourea catalyst 1 (up to 86 % yield, 93 % ee; see scheme). This reaction can be applied not only to the synthesis of the unnatural amino acid monomers but also to peptide oligomers.
Bispidine as a helix inducing scaffold: examples of helically folded linear peptides
作者:V. Haridas、Sandhya Sadanandan、M. V. S. Gopalakrishna、M. B. Bijesh、Ram. P. Verma、Srinivas Chinthalapalli、Ashutosh Shandilya
DOI:10.1039/c3cc45649h
日期:——
We designed and synthesized bispidine-anchored peptides and showed that these peptides as small as B3 (containing four chiral α-amino acid residues) adopt a right handed helical conformation. Bispidine anchored linear peptide B3 adopts a helical conformation in solution and in the solid state.
Conformationally defined piperazine bis(N-oxides) bearing amino acid derived side chains
作者:Ian A. O’Neil、Andrew J. Potter、J. Mike Southern、Alexander Steiner、James V. Barkley
DOI:10.1039/a806901h
日期:——
The preparation of a number of piperazine derivatives bearing amino acid substituents on the nitrogen is described; these compounds undergo oxidation with MCPBA to yield bis(N-oxides) in which both oxygen atoms are axially orientated and hydrogen bonded to the amide NHs, giving highly defined conformations to the molecules; the structure of the valine derivative (8c) was confirmed by X-ray analysis.
The supramolecular strategy was subjected to the asymmetrichydrogenation of 4-methylumbelliferone by electrochemical reduction in the presence of a chiral macrocyclic multifarane[3,3], which offered a l-7-hydroxy-4-methylchroman-2-one product with a chemical yield of 65% and enantioselectivity up to >99% ee. The high stability of the developed chiral supramolecular electrode guaranteed the recyclability