Enantioselective mono‐fluorination of α‐keto esters was achieved using a mildly basic palladium μ‐hydroxo complex as catalyst. Subsequent one‐pot reduction afforded optically active β‐fluoro‐α‐hydroxy esters. These compounds were then converted into β‐fluoro‐α‐amino esters, which are potentially useful in medicinal chemistry research.
A biomimetic enantioselective transamination of α-keto ester derivatives can be realized under mild conditions by using chiral quaternary ammonium arenecarboxylates in the absence of base additives. The corresponding α-aminoacids can be used as versatile intermediates for further synthetic transformations that furnish chiral pyrrolidine and octahydroindolizine derivatives.
Practical Total Syntheses of Acromelic Acids A and B
作者:Hitoshi Ouchi、Aya Asahina、Tomohiro Asakawa、Makoto Inai、Yoshitaka Hamashima、Toshiyuki Kan
DOI:10.1021/ol500529w
日期:2014.4.4
Practical total syntheses of acromelic acids A (1) and B (2), which have potent neuro-excitatory activity, were accomplished in 13 (36% total yield) and 17 steps (6.9% total yield), respectively, from 2,6-dichloropyridine (8). Regioselective transformation of symmetric 8 provided nitroalkenes 15 and 16. The pyrrolidine ring was efficiently constructed by Ni-catalyzed asymmetric conjugate addition followed by intramolecular reductive amination.
Asymmetric conjugate addition of α-keto esters to nitroolefins catalyzed by chiral CuII hydroxo complexes
As a part of our research project on hard anion-late transition metal complexes as mild acid-base catalysts, we describe herein that Cu-II hydroxo complexes having chiral N-substituted-diaminocyclohexanes are mild and selective catalysts, which are applicable to the catalytic asymmetric conjugate addition of alpha-keto esters to nitroolefins. The reaction proceeded diastereoselectively without the detectable formation of self-aldol products, affording the corresponding coupling products with anti-stereochemistry in an enantioselective manner. (C) 2010 Elsevier Ltd. All rights reserved.