Two Novel Sesquiterpenoids from the Roots of Ferula ferulaeoides (Steud.) Korov.

Two new sesquiterpenoids, ferulactones A and B ( 1 and 2 , resp.), have been isolated from the roots of Ferula ferulaeoides (Steud.) Korov . Their structures and relative configurations were established by analysis of spectroscopic data. Their absolute configuration was assigned by application of the CD technique.     

Rosellin A and B,two red diketopiperazine alkaloids from the mushroom Mycena rosella

Rosellin A and B, two red diketopiperazine alkaloids with unprecedented structures, have been isolated from the fruiting bodies of the mushroom Mycena rosella. The structures of the rosellins were mainly deduced from their 2D NMR and HRMS (ESI) spectra. Their absolute configuration was determined by comparison of the CD spectra of the rosellins with the corresponding CD spectra obtained by quantum chemical calculations. Root exposure to rosellin A led to bleaching of the leaves of Lepidium sativum plants.     

大环二萜圆盘肉芝内酯的分子构型研究

从南海圆盘肉芝软珊瑚(Sarcophyton trochliphroum)中分离得一个新的大环二萜内酯化合物-圆盘肉芝内酯(Sartrochine), 生物测定表明其具有抗肿瘤及抑菌作用。通过波谱分析, X射线单晶衍射及CD谱确定其绝对构型。     

Circular dichroism spectra of trans-chalcone epoxides

The electronic absorption and CD spectra of (−)-trans-chalcone epoxide and its derivatives with methyl and alkoxy substituents at the ortho-positions of the aromatic rings have been measured. The spectra have been assigned with help of the energies, oscillatory strengths, and rotatory strengths of the singlet transitions obtained from DFT calculations. The features of the CD spectra, indicative of the absolute configuration, are the carbonyl n–π¹ band and two further strong bands assigned to the overlapping signals of π–π¹ and n_epoxy–π¹ excitations.     

Stereoselective synthesis of the C14-C24 degraded fragment of symbiodinolide

Symbiodinolide is a polyol macrolide isolated from the marine dinoflagellate Symbiodinium sp. in 2007. The C14-C24 fragment of symbiodinolide possessing the 17R/18R/21R absolute configuration, which was obtained as one of the degraded products of symbiodinolide, was synthesized stereoselectively from cis-2-butene-1,4-diol. The detailed comparison of the synthetic product with the degraded product in the spectroscopic data confirmed that the stereostructure of the C14-C24 fragment was 17R, 18R, and 21R.     

A convenient method for the assignment of the absolute configuration to cyclic amines

We have assigned the absolute configuration to trans-2,5-dimethylpyrrolidine and trans-2,6-dimethyl-piperidine through radical chlorination in ω-1 position of optically active amines, 2 and 5, of known absolute configuration, followed by cyclization. CD curves of 1f and 4g derivatives indicate that the reaction is stereospecific. The absolute configuration of trans-2,5-dimethyl-Δ³-pyrròline has also been determined.     

Caryophyllene sesquiterpenes,chromones and 10-membered macrolides from the marine-derived fungus Pseudopestalotiopsis sp. PSU-AMF45

Three new caryophyllene sesquiterpenes, pestalotiopsins I–K, one new chromone, pseudopestalone, and one new 10-membered macrolide, decarestrictine Q, were isolated from the fermentation broth of the marine-derived fungus Pseudopestalotiopsis sp. PSU-AMF45 along with twelve known compounds. Their structures were identified by spectroscopic data including 1D and 2D NMR. The absolute configuration of pestalotiopsin I was assigned based on single-crystal X-ray diffraction crystallography whereas that of the secondary alcohol moiety in pestalotiopsin J was established by Mosher's method. For pseudopestalone, the absolute configuration was determined by ECD spectrum associated with TD-DFT calculation. The antimicrobial activity of the isolated compounds was evaluated.     

Twelve new compounds from Ligularia melanothyrsa; isolation of melanothyrsins A–E,normelanothyrsin A,and other eremophilane sesquiterpenoids

Twelve new compounds, namely, five melanothyrsins A–E (1α-angeloyloxyeremophilenolides), normelanothyrsin A (1α-angeloyloxynoreremophilenone), and six other eremophilane-type compounds, have been isolated from Ligularia melanothyrsa Hand.-Mazz. (Asteraceae), collected in the Sichuan Province of China. Six of the compounds have a 1α-angeloyloxy moiety, while the other six have no functional group at the C-1 position. The absolute configuration was also determined using CD spectra. This is the first chemical study of compounds isolated from this species.     

Scytalidamides A and B, new cytotoxic cyclic heptapeptides from a marine fungus of the genus Scytalidium

Two new cyclic heptapeptides have been isolated from the culture broth of a marine fungus, Scytalidium sp., collected from the Bahamas. The planar structures of scytalidamides A (1) and B (2) were assigned on the basis of 1D and 2D NMR spectroscopic techniques, while the absolute configuration of the amino acid residues in both molecules was determined by application of the advanced Marfey's method. The absolute stereochemistry of the uncommon 3-methylproline moiety in scytalidamide B (2) was confirmed by isolation and CD measurements, as well as application of the advanced Marfey's method. Scytalidamides A (1) and B (2) showed moderate in vitro cytotoxicity toward HCT-116 human colon adenocarcinoma with IC(50) values of 2.7 and 11.0 microM, respectively.     

Rogioldiol A,a new obtusane diterpene,and rogiolal,a degraded derivative,of the red seaweed Laurencia microcladia from II rogiolo along the coast of tuscany: A Synergism in Structural Elucidation

The structure of rogioldiol A ((?)- 1 ), isolated from the red seaweed Laurencia microcladia, was determined. Employing the exciton-coupling technique for rogioldiol A p-bromobenzoate ( 2 ), the absolute configuration at C(9) of (?)- 1 was assigned, and, together with extensive NMR experiments, the absolute configuration at C(10) and preferred conformations of (?)- 1 were determined. The absolute configuration of the hetero-substituted cyclohexane ring was deduced in analogy from the X-ray structure of 4 , a derivative of the aldehyde 3 , which was isolated from the same seaweed and is believed to be a degradation product of (?)- 1 .     

Total synthesis of epicoccamides A and D via olefin cross-metathesis

Epicoccamides A and D were synthesized through a route that utilizes fragment coupling via olefin cross-metathesis as a key step. The right-hand segment of the epicoccamides was synthesized by a tandem O-acylation–migration reaction, and the left-hand segments were stereoselectively synthesized through a modified version of Crich’s β-selective mannosylation. The previously assigned absolute configuration of the epicoccamide D was confirmed, and that of epicoccamide A was assigned as (5S,2′S) based on the NMR and CD spectra. This Letter provides the first example of the total synthesis of epicoccamide A.     

Synthesis and characterization of chiral nickel(II) Schiff base complexes and their CD spectra-absolute configuration correlations

Some nickel(II) complexes of quadridentate Schiff bases prepared from the condensation of 2 mol of 2-hydroxyacetophenone (HACP) or dehydroacetic acid (DHA) with 1 mol of optically active propylene-1,2-diamine (pn), trans-cyclohexane-1,2-diamine (chxn) or 1,2-diphenylethylenediamine (dpen) were synthesized and characterized by EA, IR, UV–vis, and CD spectra. The absolute configurations of the three complexes were determined by X-ray single crystal structure measurement and correlated with CD spectroscopy. In this study, special attention is focussed on the CD signals of the related complexes in the d–d transition region, in the hope of obtaining a tentative correlation between the CD pattern and the absolute configuration about the central metal. A new empirical rule for the assignment of the absolute configuration around the nickel ion in each complex and the handedness of the chiral diamine contained in the Schiff base ligand is put forward. In the case of tetra-coordinated pseudo-planar Ni(II) complexes, the rule can be stated as follows: (i) a positive Cotton effect in the d–d region around 550 nm is assigned to the (S)Δλ-configuration for the HACP-(S)-pn-Ni, HACP-(SS)-dpen-Ni, DHA-S-pn-Ni, and DHA-(SS)-dpen-Ni derivatives; and (ii) a concomitant inversion of the Cotton effect in the same range is assigned to the (S)Λδ-configuration for the HACP-(SS)-chxn-Ni and DHA-(SS)-chxn-Ni derivatives.     

Fuligoic acid, a new yellow pigment with a chlorinated polyene-pyrone acid structure isolated from the myxomycete Fuligoseptica f. flava

Fuligoic acid (1), a new yellow pigment with a chlorinated polyene-pyrone acid structure, was isolated from field-collected fruit bodies of the myxomycete Fuligoseptica f. flava, and its structure was elucidated by spectral data, including its absolute configuration based on CD data.     

neo‐Clerodane Diterpenoids from the Aerial Part of Scutellaria barbata

Three new neo‐clerodane diterpenoids, barbatellarines C–E ( 1 – 3 ), were isolated from the CHCl₃‐soluble fraction of the aerial part of Scutellaria barbata. Their chemical structures were elucidated by detailed analysis of NMR and MS data. Compounds 1 and 2 were C(13) epimers, which was confirmed by an NOE difference experiment and the NOESY spectrum. The relative configuration was determined on the basis of the ¹H‐NMR J‐value and NOE data, while the absolute configuration of the previously isolated analogue, barbatellarine B ( 4 ), as a representative member of the group, was assigned by CD analysis.     

Biocatalytic deracemization of alkyl-2-hydroxy-4-arylbut-3-ynoates using whole cells of Candida parapsilosis ATCC 7330

Racemic alkyl-2-hydroxy-4-arylbut-3-ynoates were deracemized to the (S)-alkyl-2-hydroxy-4-arylbut-3-ynoates in excellent enantiomeric excesses (up to >99%) and good isolated yields (up to 81%) with the biocatalyst Candida parapsilosis ATCC 7330. The absolute configuration of the resulting enantiomer was assigned by ¹H NMR using Mosher’s method.     

Crystal and molecular structure of the levorotatory (1R,2S)-ephedrinium (S)-t-butylsulfinylacetate: a definitive proof of the absolute configuration of enantiomeric t-butyl methyl sulfoxides

The levorotatory enantiomer of t-butylsulfinylacetic acid 3 was obtained in the reaction of the α-carbanion of (+)-t-butyl methyl sulfoxide 1 with carbon dioxide. The same enantiopure form of the acid 3 was isolated from its diastereomerically pure levorotatory salt 5 with (−)-(1R,2S)-ephedrine. The structure of this salt was determined by X-ray analysis and the absolute configuration (S) at sulfur was ascribed to the t-butylsulfinylacetate anion. Consequently, the absolute configuration (S) was assigned to the acid (−)-3 and its precursor (+)-t-butyl methyl sulfoxide 1.     

Gelegamines A-E: five new oxindole alkaloids from Gelsemium elegans

Five new oxindole alkaloids, gelegamines A-E (1-5), were isolated from the roots of Gelsemium elegans. Their structures were extensively elucidated on the basis of spectroscopic analysis. Among them, the epoxy ring (C-19/C-20) of gelegamine A (1) was assigned as α-orientation by ROESY experiment and DFT method at B3LYP/6-31g(d) level, and gelegamine B (2) is the first humantenine-type alkaloid with 19-(E) ethylidene configuration. The absolute configurations of gelegamines A-E (1-5) were established on biosynthetic consideration coupled with CD experiments.     

Secu'amamine A, a novel indolizidine alkaloid from Securinega suffruticosa var. amamiensis

A novel indolizidine alkaloid, secu'amamine A (1), was isolated from the leaves and twigs of the medicinal plant, Securinega suffruticosa var. amamiensis together with securinine (2). The structure and relative stereochemistry of 1 was elucidated by spectroscopic data and its absolute configuration was assigned on the basis of the OMe-madelate method.     

1H and 13C NMR assignments for 6-demethylvermistatin and two penicillide derivatives from the mangrove fungus Guignardia sp. (No. 4382) from the South China Sea

One new compound 6-demethylvermistatin (1), together with two known compounds, the penicillide derivatives (2) and (3) were isolated from the mangrove fungus Guignardia sp. No. 4382 obtained from the South China Sea. Their structures were assigned using high-resolution electron ionization mass spectrometry(HREIMS), (1)H and (13)C NMR spectra, DEPT, and by 2D COSY, HMQC, and HMBC experiments. The absolute configuration of 1 was established by comparison of its CD with that of vermistatin.     

Cylindromicin from Arctic-Derived Fungus Tolypocladium sp. SCSIO 40433

The fungus strain SCSIO 40433 was isolated from an Arctic-derived glacier sediment sample and characterized as Tolypocladium cylindrosporum. A new compound, cylindromicin (1), and seven known secondary metabolites (2–8) were isolated from this strain. The chemical structures of these compounds were elucidated by comprehensive spectroscopic analyses. Cylindromicin (1) featured a 3,4-dihydro-2H-pyran skeleton. The absolute configuration of compound 1 was assigned via interpretation of key Nuclear Overhauser Effect Spectroscopy (NOESY) correlations and Electronic Circular Dichroism (ECD) calculation. Cylindromicin (1) exhibited significant tyrosinase inhibition activity. This study highlights Polar fungi as a potential resource for new bioactive natural products.