Highly oxidized graphene oxide as carbocatalyst for the multicomponent synthesis of triazoloquinazolines

The Brønsted acidity of graphene oxide (GO) materials has shown promising activity in organic synthesis. However, the roles and functionality of Lewis acid sites remain elusive. Herein, we report a carbocatalytic approach utilizing both Brønsted and Lewis acid sites in GOs as heterogeneous promoters in a series of multicomponent synthesis of triazoloquinazolinone compounds. The GOs possessing the highest degree of oxidation, also having the highest amounts of Lewis acid sites, enable optimal yields (up to 95%) under mild and non-toxic reaction conditions (85oC in EtOH). The results of FT-IR spectroscopy, temperature-programmed decomposition mass spectrometry, and X-ray photoelectron spectroscopy identified that the apparent Lewis acidity via basal plane epoxide ring-opening, on top of the saturated Brønsted acidic carboxylic groups, is responsible for the enhanced carbocatalytic activities involving Knoevenagel condensation pathway. Recycled GO can be effectively regenerated to reach 97% activity of fresh GO, supporting the recognition of GO as pseudocatalyst in organic synthesis

Triterpenes and sterol from Hoya mindorensis

Chemical investigation of the dichloromethane extract of the air-dried roots of Hoya mindorensis Schlechter afforded lupenone (1) and lupeol (2). The leaves yielded 2, squalene (3) and β-sitosterol (4), while the stems afforded betulin (5). The structures of 1-5 were identified by comparison of their 1H and/or 13C NMR data with those reported in literature

Terpenoids and sterols from Hoya multiflora Blume

Chemical investigation of the dichloromethane extracts of Hoya multiflora Blume led to the isolation of lupeol (1a), α-amyrin (1b), β-amyrin (1c), lupeol acetate (2a), α-amyrin acetate (2b), and β-amyrin acetate (2c) from the stems; and 1b, bauerenol (3), squalene (4), lutein (5), β-sitosterol (6a), and stigmasterol (6b)from the leaves. The structures of 1-6 were identified by comparison of their 1H and/or13C NMR data with those reported in the literature. © 2015 Virgilio Ebajo Jr. et al

Chemical constituents of Hoya buotii Kloppenb

Chemical investigation of the dichloromethane extracts of Hoya buotii Kloppenb. afforded taraxerone (1), taraxerol (2), a mixture of ß-sitosterol (3a) and stigmasterol (3b) in about 2:1 ratio, and a mixture of α-amyrin cinnamate (4a) and ß-amyrin cinnamate (4b) in about 1:2 ratio from the stems; 1, 2, and 3a from the roots; a mixture of 4a and 4b in about 3:2 ratio from the flowers; and 3a, squalene (5) and saturated hydrocarbons from the leaves. The structures of 1-5 were identified by comparison of their NMR data with those reported in the literature. © 2015 Virgilio D. Ebajo Jr. et al

Sterols and lipids from Pleurotus florida

Chemical investigation of the dichloromethane extract of the fruiting bodies of Pleurotus floridaled to the isolation of ergosterol (1), ergosterol peroxide (2), cerevisterol(3), a mixture of palmitic acid and stearic acid, linoleic acid, and oleic acid in about 1.5:1:0.5 ratio, and dilinoleoyloleoylglycerol. The structures of these compounds were identified by comparison of their NMR data with literature data

Secondary metabolites from Caulerpa racemosa

Chemical investigation of the dichloromethane extract of Caulerparacemosaled to the isolation of α-tocopherol (1),squalene (2), β-sitosterol (3), chlorophyll a (4), and oleic acid (5). The structures of these compounds were identified by comparison of their NMR data with those reported in the literature

Secondary metabolites from Hypnea nidulans Setchell

Chemical investigation of the dichloromethane extract of Hypnea nidulans Setchell has led to the isolation of monogalactosyl diacylglycerols (1) and zeinoxanthin (2). The structure of 1 was elucidated by extensive 1D and 2D NMR spectroscopy. The structure of 2 was identified by comparison of its NMR data with those reported in the literature

Chemical constituents of Hypnea nidulans setchell

Chemical investigation of the dichloromethane extract of Hypnea nidulans Setchell led to the isolation of squalene (1), β-sitosterol (2), a mixture of ursolic acid (3) andoleanolic acid (4) in a 3:1 ratio, chrorophyll a (5), and hydrocarbons. The structures of these compounds were identified by comparison of their NMR data with those reported in the literature