Aldol reactions of ketal-protected tartrate ester enolates. Asymmetric syntheses and absolute stereochemical assignments of phospholipase A2 inhibitors cinatrin C1 and C3
摘要:
An efficient approach to the syntheses of cinatrins C-1 and C-3 has been developed and used to establish the absolute configurations of these natural products. The construction of each molecule has been achieved in a five-step reaction sequence (overall yield 43% for cinatrin C-1, 33% for cinatrin C-3) from the di-tert-butyl ester of (R,R)-tartaric acid. The two contiguous, quaternary chiral centers in the cinatrin skeleton are constructed via a diastereoselective, titanium-mediated aldol coupling of a tartrate-derived silylketene acetal and an achiral alpha-ketoester. This bond construction proceeds with excellent diastereoselectivity for a variety of aldehyde and alpha-ketoester substrates. (C) 1997 Elsevier Science Ltd.
AbstractPalladium‐catalyzed enantioselective C(sp3)−H functionalization reactions has attracted considerable attention due to its ability for the synthesis of enantiomerically enriched molecules and stimulation of novel retrosynthetic disconnections. Understanding the reaction mechanism, especially the stereochemical process of the reaction, is crucial for the rational design of more efficient catalytic systems. Previously, we developed a Pd(II)/sulfoxide‐2‐hydroxypridine (SOHP) catalytic system for asymmetric C(sp3)−H functionalization reactions. In this study, we focused on unraveling the chemistry of chiral palladacycles involved in the Pd(II)‐catalyzed enantioselective C(sp3)−H functionalization. We have isolated key palladacycle intermediates involved in the enantioselective β‐C(sp3)−H arylation of carboxylic acids catalyzed by the Pd(II)/SOHP system. These palladacycles, exhibiting ligand‐induced chirality, provided a significant opportunity to investigate the stereochemical process and the ligand effect in this asymmetric C−H functionalization. Our investigation provided direct evidence for the C−H palladation step as the enantioselectivity‐determining step, which forms diastereomeric palladacycles that exhibited preservation of chirality in the functionalization step. DFT calculations provided insights into the chiral induction in palladacycle formation. This work highlights the value of chiral palladacycle chemistry in offering mechanistic insights into the Pd(II)‐catalyzed asymmetric C(sp3)−H functionalization reactions.
The invention provides an antibacterial compound of formula (I) or a salt thereof, as well as an antibacterial compound of formula (II) or a salt thereof, wherein R
1
, R
2
, W, X, Y and n have any of the values defined in the specification.
Asymmetric Synthesis of the Squalene Synthase Inhibitor Zaragozic Acid C
作者:David A. Evans、James C. Barrow、James L. Leighton、Albert J. Robichaud、Michael Sefkow
DOI:10.1021/ja00105a085
日期:1994.12
Merck2 and Glaxo,' a number of closely related structures sharing the common 2,8-dioxabicyclo[3.2. lloctane core have been isolated and characterized to date. The purpose of this communication is to disclose a route to the synthesis of zaragozicacid C (1)5 which is amenable to the synthesis of the other members of this family of natural products.6
AMPHIPHILIC MACROMOLECULES AND METHODS OF USE THEREOF
申请人:RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY
公开号:US20160068467A1
公开(公告)日:2016-03-10
Certain embodiments of the invention provide a compound of formula (I):
A-X—Y—Z—R
1
(I),
or a salt thereof, wherein A, X, Y, Z and R
1
have any of the values defined in the specification, and methods of use thereof. For example, certain embodiments of the invention provide a method for inhibiting atherosclerosis or atherosclerotic development in a mammal, comprising administering to the mammal an effective amount of a compound of formula (I), or a pharmaceutically acceptable salt thereof.
Facile Syntheses of (2R,3R)-(−)- and (2S,3S)-(+)-Chicoric Acids
作者:He Zhao、Terrence R. Burke
DOI:10.1080/00397919808005946
日期:1998.2
Abstract Practical and efficient syntheses of (2R, 3R)-(−)- and (2S, 3S)-(+)-chicoric acids are reported, which may be amenable to analogue preparation.
[EN] ACETYLATED AND RELATED ANALOGUES OF CHICORIC ACID AS HIV INTEGRASE INHIBITORS<br/>[FR] ANALOGUES ACETYLES ET CORRESPONDANTS D'ACIDE CHICORIQUE EN TANT QU'INHIBITEURS DE L'INTEGRASE DU VIH
申请人:US HEALTH
公开号:WO2000063152A1
公开(公告)日:2000-10-26
Chicoric acid analogues and derivatives have activity against HIV-1 integrase. The structural features that are required for this activity are elucidated by assaying these analogues and derivatives against HIV-1 integrase. Furthermore, methods of synthesis of the enantiomers of chicoric acid itself, as well as its analogues and derivatives, are disclosed. Additionally, methods of use of chicoric acid analogues and derivatives to inhibit HIV-1 integrase are disclosed, as are compositions comprising chicoric acid analogues and derivatives.