Enantioselective decarboxylative Mannich reaction of ß-keto acids with C-alkynyl N-Boc N,O-acetals: access to chiral ß-keto propargylamines.

The chiral keto-substituted propargylamines are an essential class of multifunctional compounds in the field of organic and pharmaceutical synthesis and have attracted considerable attention, but the related synthetic approaches remain limited. Therefore, a concise and efficient method for the enantioselective synthesis of ß-keto propargylamines via chiral phosphoric acid-catalyzed asymmetric Mannich reaction between ß-keto acids and C-alkynyl N-Boc N,O-acetals as easily available C-alkynyl imine precursors has been demonstrated here, affording a broad scope of ß-keto N-Boc-propargylamines in high yields (up to 97%) with generally high enantioselectivities (up to 97 : 3 er).

Penisarins A and B, Sesquiterpene Coumarins Isolated from an Endophytic Penicillium sp.

Penisarins A (1) and B (2), sesquiterpene coumarins with an unusual tricyclic sesquiterpene system, were isolated from endophytic Penicillium sp. KMU18029. Their structures were elucidated on the basis of spectroscopic methods, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Compound 2 showed significant cytotoxicities against two human cancer cell lines, HL-60 and SMMC-7721, with IC50 values of 3.6 ± 0.2 and 3.7 ± 0.2 µM, respectively.

Asymmetric Synthesis of Triphenylmethanes via Organocatalytic Regio- and Enantioselective Friedel-Crafts Alkylation of Aniline Derivatives.

Herein, we described a highly regio- and enantioselective Friedel-Crafts alkylation of aniline derivatives with in situ generated ortho-quinone methides enabled by chiral phosphoric acid, furnishing a wide range of enantioenriched triarylmethanes bearing three similar benzene rings in high yields (up to 98%) with excellent stereoselectivities (up to 98% ee). Furthermore, the large-scale reactions and diversified transformations of product demonstrate the practicality of the protocol. Density functional theory calculations elucidate the origin of the enantioselectivity.

Comparative enantioseparation of seven triazole fungicides on (S,S)-Whelk O1 and four different cellulose derivative columns.

The comparative enantioseparation of seven chiral triazole fungicides on a Pirkle type (S,S)-Whelk O1 chiral column and four different cellulose derivative columns, namely cellulose tribenzoate (CTB), cellulose tris(4-methylbenzoate) (CTMB), cellulose triphenylcarbamate (CTPC), and cellulose tris(3,5-dimethylphenyl carbamate) (CDMPC), in normal phase mode is described. The seven triazole fungicides investigated were tebuconazole, hexaconazole, myclobutanil, diniconazole, uniconazole, paclobutrazol, and triadimenol. The chiral separation of each solute was investigated with ethanol, n-propanol, iso-propanol, and n-butanol, respectively, as polar modifier in the hexane mobile phase. The results revealed that (S,S)-Whelk O1 was less than universal and only hexaconazole and triadimenol underwent enantioseparation. Among the self-prepared cellulose derivative columns used, the enantiomeric resolution capacities for the studied analytes generally decreased in the order CDMPC > CTPC > CTMB > CTB. The best enantioseparation of the analytes was mostly obtained on CDMPC and none of them were enantioseparated on CTB. The chiral recognition mechanisms between the analytes and the chiral selectors are discussed.