RESUMO
A highly effective asymmetric version of α-cyanation of ß-keto esters and amides was developed with a Lewis-acid catalyst. Thus, by using 10â mol % of a tridentate bisoxazoline-zinc(II) complex as the catalyst, a series of chiral nitriles containing a quaternary carbon center were obtained in excellent enantioselectivities (up to 97 % enantiomeric excess) and up to 95 % yield in the presence of 4â Å molar sieve at room temperature. For the first time, mild and active 4-acetylphenyl cyanate was used instead of cyano-hyperiodinate as the cationic cyano source for catalytic asymmetric α-cyanation.
RESUMO
Seven sesquiterpene derivatives, including chaetopenoids A-F and dendryphiellin A1, and 6-methyl-(2E, 4E, 6S) octadienoic acid were isolated from the culture broth of Chaetoconis sp. FT087. Their structures were determined through the analysis of HRMS and NMR spectroscopic data. The absolute configurations of chaetopenoids A-D were elucidated by comparison of their CD and optical rotation data with those in the literature. Chaetopenoids A-C and E belong to the eremophilane type of sesquiterpenoids, while chaetopenoids D and F and dendryphiellin A1 have a trinor-eremophilane skeleton. All compounds were tested against A2780 and cisplatin resistant A2780CisR cell lines, and dendryphiellin A1 was moderately active with IC50 values of 6.6 and 9.1 µg/mL, respectively.
Assuntos
Ascomicetos/química , Sesquiterpenos/isolamento & purificação , Havaí , Humanos , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Sesquiterpenos/químicaRESUMO
An endophytic fungus Paraphaeosphaeria neglecta FT462 isolated from the Hawaiian-plant Lycopodiella cernua (L.) Pic. Serm produced one unusual compound (1, paraphaeosphaeride A) with the 4-pyranone-γ-lactam-1,4-thiazine moiety, along with two new compounds (2 and 3, paraphaeosphaerides B and C, respectively) and the known compound (4). Compounds 1-3 were characterized by NMR and MS spectroscopic analysis. The absolute configuration of the 3-position of compound 1 was determined as S by electronic circular dichroism (ECD) calculations. Compound 3 also showed STAT3 inhibition at 10 µM.
Assuntos
Fungos/química , Lactamas/química , Lactamas/síntese química , Plantas/química , Pironas/química , Pironas/síntese química , Tiazinas/química , Tiazinas/metabolismo , Fungos/isolamento & purificação , Havaí , Lactamas/isolamento & purificação , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Pironas/isolamento & purificação , EstereoisomerismoRESUMO
A series of novel 2',3'-diethanethio-2',3',5'-trideoxy-5'-triazoloribonucleosides was synthesized in excellent yields and their antitumor activity was evaluated. These nucleoside analogues with aromatic substituted triazole rings showed significantly improved activity towards a broad range of tumor cell lines and those without arene substitutes were inactive.
Assuntos
Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Nucleosídeos/síntese química , Nucleosídeos/farmacologia , Antineoplásicos/química , Linhagem Celular Tumoral , Humanos , Concentração Inibidora 50 , Nucleosídeos/químicaRESUMO
A new sesquiterpene lactone with an unusual sulfonic acid group, 13-sulfo-dihydrodehydrocostus lactone (1), was isolated from the roots of Saussurea lappa C. (Compositae), together with a known lignan (2). The structure of 1 was characterized on the basis of spectral evidence including 2DNMR studies. Compound 2 was obtained from this plant for the first time.
Assuntos
Asteraceae/química , Lactonas/química , Sesquiterpenos/química , Ácidos Sulfônicos/química , Análise EspectralRESUMO
Two new sesquiterpene lactones with the unusual sulfonic acid group, 13-sulfo-dihydrosantamarine (1) and 13-sulfo-dihydroreynosin (2), have been isolated from the roots of Saussurea lappa C. Their structures, including the absolute configurations, were elucidated by spectroscopic methods.
Assuntos
Lactonas/química , Saussurea/química , Sesquiterpenos/química , Lactonas/isolamento & purificação , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Sesquiterpenos/isolamento & purificação , Sesquiterpenos de EudesmanoRESUMO
A new monoterpene, eucommidiol (1), was isolated from the bark of Eucommia ulmoides Oliv. (Eucommiaceae), together with a known compound 1,4a,5,7a-tetrahydro-7-hydroxymethyl-cyclopenta[c]pyran-4-carboxylic methyl ester. The structure of 1 was characterized as 6,6a-di(hydroxymethyl)-3,3a,4,6a-tetrahydro-2H-cyclopenta[b]furan-2-one on the basis of chemical and spectral evidence including 2DNMR studies.