Total synthesis of the marine cytotoxic caulibugulones A-D

We report the first total synthesis of the cytotoxic marine alkaloids caulibugulone A-D. This synthesis confirmed the assigned structures and provided sufficient material for further biological testing.     

电阻传感器信号测量的自校正方法

本文介绍了电阻传感器在信号测量中采用自校正技术的测量方法     

Unprecedented C_(19)-diterpenoid alkaloid glycosides from an aqueous extract of “fu zi”: Neoline 14-O-L-arabinosides with four isomeric L-anabinosyls

Four structurally unprecedented aconitane-type C_(19)-diterpenoid alkaloid glycosides with isomeric arabinosyls, named aconicarmichosides A–D(1–4), were isolated from an aqueous extract of "fu zi", the lateral roots of Aconitum carmichaelii. Their structures were determined as neoline 14-O-a-and 14-O-b-L-arabinopyranosides(1 and 2) and 14-O-a-and 14-O-b-L-arabinofuranosides(3 and 4), by spectroscopic and chemical methods including 2D NMR experiments and acid hydrolysis. Compounds 1–4 represent the first examples of glycosidic diterpenoid alkaloids.     

Saiyutones A-D: four new unusual biflavones from Desmos chinensis

Four new unusual biflavones, saiyutones A-D, were isolated from the leaves of Desmos chinensis together with 16 known compounds. Their structures were determined on the basis of UV, IR, NMR, and MS analysis, and by comparison of their spectroscopic data with those reported. Saiyutones A and B had a unique biflavone skeleton with a 3-6″ linkage through a methylene group. It was proposed that the formation of a cyclic hemiketal was the key step in the biosynthetic pathway of saiyutones C and D.     

Thioquinomycins A-D,novel naphthothiophenediones from the marine-derived Streptomyces sp. SS17F

Thioquinomycins A-D (1–4), four novel naphthothiophenediones were isolated from the rice-based medium of the marine-derived Streptomyces sp. SS17F. Their structures were elucidated by spectroscopic methods and HRESIMS data. The absolute configurations of all the compounds were elucidated by X-ray diffraction analysis, ECD and Mosher's method combined with ¹⁹F-NMR. Compounds 1–4 showed moderate cytotoxicity against NCI-H1975 with IC₅₀ values from 17.5 to 50?μM. In addition, compounds 1–4 also exhibited inhibitory activities against PKCα and ROCK2 protein kinase.     

Six insecticidal isoryanodane diterpenoids from the bark and twigs of Itoa orientalis

Four rare isoryanodane diterpenoids namely itols A-D (1-4) and two isoryanodane glucosides (5 and 6) were isolated from the bark and twigs of Itoa orientalis. Their structures were determined by NMR and MS techniques and the structure of 1 was confirmed by a single-crystal X-ray diffraction. These six diterpenoids obviously showed insecticidal activity against Spodoptera exigua, with LC₅₀ 28.62 ppm for 1 and 52.76 ppm for 2, respectively. In anti-inflammatory assay, compounds 1 and 4-6 showed anti-COX-2 activity, with inhibitory rates of 54.7-78.3% at 10 μM.     

Sphenalactones A-D, a new class of highly oxygenated trinortriterpenoids from Schisandra sphenanthera

Four novel highly oxygenated trinortriterpenoids, sphenalactones A-D (1-4), were isolated from the leaves and stems of Schisandra sphenanthera and their structures were elucidated by extensive analysis of 1D and 2D NMR data. Compounds 1-4 featured a C₂₇ backbone and showed anti-HIV-1 activity with EC₅₀ values in the range of 35.5-89.1 μg/mL with low cytotoxicity against C8166 cells (CC₅₀ > 200 μg/mL).     

Structures of new alkaloids sessilifoliamides A-D from Stemona sessilifolia

Four new Stemona alkaloids, sessilifoliamides A-D (1-4), were isolated from the roots of Stemona sessilifolia, along with five known alkaloids, stenine (5), 2-oxostenine (6), stemoninoamide (7), tuberostemonone (8), and neotuberostemonol (9). The structures and absolute configurations of the new alkaloids were determined by the spectral studies (HRMS, IR, ¹H, ¹³C, and 2D NMR), single-crystal X-ray analyses, and chemical correlations. The absolute configuration of 7 was also determined by the modified Mosher's method.     

Efficient total syntheses of louisianins C and D

An efficient synthetic route for the preparation of louisianins C and D was developed starting with the commercially available 4-cyanopyridine. Louisianins C and D were synthesized in seven steps and with overall yields 22% and 20%, respectively, following a novel cyclization-decarboxylation sequence involving 4-bromo-6,7-dihydrocyclopenta[c]pyridin-5-one as the key intermediate.     

Phomachalasins A-D, 26-oxa[16] and [15]cytochalasans produced by Phoma exigua var. exigua, a potential mycoherbicide for Cirsium arvense biocontrol

Phoma exigua var. exigua, a fungal pathogen isolated from Cirsium arvense and Sonchus arvensis, proposed as a biocontrol agent of this noxious perennial weeds, produces in liquid and solid cultures different phytotoxic metabolites with potential herbicidal activity. The phytotoxic cytochalasins B, F, Z2, and Z3 and deoxaphomin were previously identified together with p-hydroxybenzaldehyde. Using spectroscopic methods, four new cytochalasins, termed phomachalasins A-D, were isolated and characterized as three new closely related 26-oxa[16] and one new [15]cytochalasans. They belong to a new subgroup of cytochalasans bearing a 1,2,3,4,6,7-hexasubstituted bicycle[3.2.0]heptene joined to the macrocyclic ring. None of the four new metabolites showed phytotoxic or antimicrobial activity. The lack of both phytotoxic and antimicrobial activities showed by all phomachalasins A-D was probably due to the strong modification of both functionalities and conformational freedom of the macrocyclic ring caused by its junction with the bulky and quite rigid new bicycle, namely bicycle[3.2.0]heptene.