Xiao-Zhang Feng

Maremycins C and D, New Diketopiperazines, and Maremycins E and F, Novel Polycyclicspiro-Indole Metabolites Isolated fromStreptomycessp.

New diketopiperazines, named maremycins C1/C2 (1a/1b) and D1/D2 (2a/2b), as well as the novel spiro-indoles, maremycins E (3) and F (4), have been detected alongside the known maremycin B (6) in the culture broth of Streptomyces sp. (strain GT 051237) by chemical screening. The structures have been determined by detailed NMR spectroscopic investigations of the isolated metabolites. Maremycins C1/C2 (1a/1b) as well as D1/D2 (2a/2b) are diastereomers and were identified as mixtures. Structurally, maremycins C1/C2 (1a/1b) are the diastereomers of the sulfur oxidation products of maremycin B (6), while D1/D2 (2a/2b) are the demethylmercapto analogues of maremycins A (5) and B (6), respectively. Maremycins E and F possess a novel structural skeleton, where a spiro moiety is formed between the 6-position of the cyclopenta[f]quinoxaline moiety and the 3′-position of the indol-2-one moiety of the initial diketopiperazine product.

Three New Triterpenoids from Fuscoporia Obliqua

Abstract Three new lanostane triterpenoids, fuscoporianol A (1), B (2), and C (3) were isolated from the petroleum ether extracts of Fuscoporia obliqua and their structures have been determined on the basis of chemical, spectroscopic methods and X-ray crystallographic analysis as 25-methoxy-21, 22-cyclolanosta-8-ene-3β, 21α-diol (1), 3β, 22α-dihydroxy-lanosta-8, 23E-diene-25-peroxide (2), 3β, 22α, 25-trihydroxy-lanosta-8, 23E-diene (3).

Rakicidin C, A New Cyclic Depsipeptide from Streptomyces sp.

Chemical screening of extracts of Actinomycetes strains has led to the detection, isolation, and structure elucidation of the new cyclic depsipeptide rakicidin C (1). The secondary metabolite from Streptomyces sp. (strain GT 61042) is built-up from glutamine, N-methyl glycine, 4-amino-(2E,4)-pentadienoic acid, and 3-hydroxy-2,4,6,8-tetramethylnonanoic acid.

New 2-o-methylrhamno-isoflavones from Streptomyces sp.

Chemical screening with extracts of Actinomycetes strains resulted in the detection, isolation and structure elucidation of five new isoflavone glycosides from Streptomyces sp. (GT 51173): 5-O-α-lrhamnopyranosyl genestein (genestein G1, 1), 5-O-α-lrhamnopyranosyl-7-O-[2-O-(methyl)-α-lrhamnopyranosyl] genestein (genestein G2, 2), 7,4′-O-di-[2-O-(methyl)-α-lrhamnopyranosyl daidzein (daidzein G1, 3), 6-O-methyl-7-O-[2-O-(methyl)-α-l-rhamnopyranosyl daidzein (daidzein G2, 4) and 7-O-[2-O-(methyl)-α-lrhamnopyranosyl daidzein (daidzein G3, 5). As a striking structural feature, 2-5 bear one or two α-lrhamnopyranosyl sugar moieties with methoxy groups in an axial position at C-2.

Secondary metabolites from fungus Fomes cajanderi

As a part of our systematic investigation of chemical constituents of Polyporaceous family fungi (Basidiomycetes), we studied the fungus of Fomes cajanderi P. Karst collected from Jiling province, China in 1997, and isolated 15 compounds, of which, compound 5 is a naturally occurring new metabolite, while 9, 11 and 12 are new derivatives. Their structures were identified by means of MS, NMR spectra and X-ray crystallographic analysis.

NEW EUDESMENOIC ACID METHYL ESTER FROM ARTEMISIA SELENGENSIS

The aerial parts of Artemisia selengensis yielded a new eudesmenoic acid methyl ester together with a known eudesmanolide. The structures were elucidated by spectroscopic methods. The relative stereochemistry of the title compound was further supported by the result of a successful single-crystal X-ray diffraction analysis.

Mongolenin: A New Triterpene from Artemisia Mongolica

Abstract A new triterpene, 13β-methyl isomer of bauerenol acetate, named mongolenin, has been isolated from the aerial parts of Artemisia mongolica. The structure was elucidated by spectroscopic methods. Its 13C- and 1H-NMR chemical shifts have been assigned unambiguously on the basis of detailed 2D-NMR analyses.

Streptoketol A and B, New Secondary Metabolites with DNA-Binding Properties

Abstract The new natural products, streptoketol A (1) and B (2), were discovered by chemical screening as secondary metabolites of Streptomyces sp. (strain GT 051243). The absolute stereochemistry of 1 was deduced by Helmchens method and CD spectroscopy. The streptoketols show DNA-binding properties which were observed with a recently developed method using thin-layer chromatography (bio-molecular-chemical screening).