A new catalytic asymmetric Henry reaction has been developed that uses a C(1)-symmetric chiral aminopyridine ligand derived from camphor and picolylamine. A variety of aromatic, heteroaromatic, aliphatic, and unsaturated aldehydes react with nitromethane and other nitroalkanes in the presence of DIPEA (1.0 equiv), Cu(OAc)(2)*H(2)O (5 mol %), and an aminopyridine ligand (5 mol %) to give the expected products in high yields (up to 99 %), moderate-to-good diastereoselectivites (up to 82:18), and excellent enantioselectivities (up to 98 %). The reaction is air-tolerant and has been used in the synthesis of the antifungal agent miconazole.
2-Alkenoyl pyridine N-oxides are introduced as a new kind of efficient dienophiles for the Cu(II)-bis(oxazoline) (BOX) catalyzed enantioselective Diels-Alder reaction affording higher reactivity and enantioselectivity (ee's up to 96%) than the corresponding nonoxidized 2-alkenoyl pyridines.
The dibenzo[b,f][1,4]oxazepine scaffold is a privileged structure in medicinal chemistry that displays a wide variety of biological and pharmacological activities. However, catalytic asymmetric methodologies for the synthesis of chiral dibenzo[b,f][1,4]oxazepine derivatives are scarce in the literature. This microreview presents an overview of enantioselective reactions in which these cyclic seven‐membered imines are used as electrophiles, including their substrate scope, limitations and application to the synthesis of related compounds.
The aerial parts of Centaurea achaia afforded, in addition to several known sesquiterpene lactones and sesquiterpene hydroxyesters, a new germacranolide and a new elemanolide. Their structures were determined as the 8a-0-(4,5-dihydroxy-tigloyloxy) esters of salonitenolide and of 11,13-dihydromelitensin, respectively. The in vitro antifungal activity of most compounds was tested against nine fungal species using the micro-dilution method. All the tested compounds showed strong antifungal activity.
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