Preparation of axially chiral quinolinium salts related to NAD+ models: new investigations of these biomimetic models as ‘chiral amide-transferring agents’
The general purpose of this work is to investigate the potential of biomimetic NAD(+) models as 'nucleophile-transferring agents' with the ultimate motivation to develop new synthetic tools. This first report focuses on the preparation of an axially chiral quinolinium salt 8. A preliminary investigation of these NAD(+) analogues as 'chiral amide-transferring agents' is reported herein. The synthesis of the desired quinolinium salt 8 was first attempted via a Friedlander approach. Given the poor reproducibility of this first synthetic route, a second strategy making use of an intramolecular nickel-catalyzed coupling was developed with success, furnishing the quinolinium salt 8 in 12% overall yield. The potential of the quinolinium salt 8 as a 'chiral amide-transferring agent' was then investigated. Regioselective 1,4-addition of benzylamine and piperidine produced, respectively, adducts 18a and 18b with high diastereoselectivity (de >95%). The resulting 'chiral masked-amide' 18b was reacted with various activated aryl esters affording the corresponding atropisomeric amide 20 with modest atropenantioselectivity (ee = 2-20%). (C) 2004 Elsevier Ltd. All rights reserved.
Highly reactive and stereospecific reaction of quinoline-type NADH model compounds with methyl benzoylformate
NADH model compounds with a dihydroquinoline ring can reduce methylbenzoylformate with very high reactivity and stereospecificity. Chiral column HPLC is effective in the separation and analysis of enantiomers of NADH and NAD model compounds, respectively.
syn/anti ratio, which indicate the orientation between carbonyl oxygen and hydrogen at the 4-position, are significantly affected by addition of magnesium ion. In the rotational transition state, the double-bond character of the C(carbonyl)-N(amide) bond is disrupted judging from the activation parameters. The oxidation of chiral 5 with p-benzoquinone in the presence of magnesium ion catalyst gave predominantly