Semipinacol rearrangement of a bicyclo[7.2.0]undecane framework into a bicyclo[6.3.0]undecane skeleton: A model study on the biosynthesis of seiridiasteriscane A

2021 ◽  
Author(s):  
Osamu Ishibashi ◽  
Mami Nishiyama ◽  
Eunsang Kwon ◽  
Masaru Hashimoto ◽  
Shigefumi Kuwahara ◽  
...  
Keyword(s):  
Silica Gel ◽  
Biosynthetic Pathway ◽  
Ring System ◽  
Model Study ◽  
Semipinacol Rearrangement

Abstract Seiridiasteriscane A is an asteriscane-type sesquiterpenoid bearing a trans-fused bicyclo[6.3.0]undecane skeleton. Although its biosynthesis has been proposed to involve a semipinacol rearrangement of a putative intermediary acetate bearing a bicyclo[7.2.0]undecane ring system (presumably derived from co-isolated pestalotiopsin M) followed by epimerization of the resulting cis-fused seiridiasteriscane B, such a type of semipinacol rearrangement has never been reported so far. Our model study revealed that a 1-hydroxybicyclo[7.2.0]undecan-2-yl acetate underwent a smooth and stereospecific semipinacol rearrangement with the assistance of Et2AlCl to give the corresponding bicyclo[6.3.0]undecane-9-one. In addition, the resulting cis-fused 5,8-bicyclic ketone was partially epimerized to the corresponding trans-fused ketone by prolonged adsorption onto a silica gel plate. These results may support a recently proposed biosynthetic pathway of seiridiasteriscane A.

scholarly journals Aspergiloid I, an unprecedented spirolactone norditerpenoid from the plant-derived endophytic fungus Aspergillus sp. YXf3

2014 ◽  
Vol 10 ◽  
pp. 2677-2682 ◽  
Author(s):  
Zhi Kai Guo ◽  
Rong Wang ◽  
Wei Huang ◽  
Xiao Nian Li ◽  
Rong Jiang ◽  
...  
Keyword(s):  
Endophytic Fungus ◽  
Spectroscopic Data ◽  
Biosynthetic Pathway ◽  
Culture Broth ◽  
Ring System ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anti Oxidant ◽  
Inhibitory Activities ◽  
Aspergillus Sp

An unusual C18 norditerpenoid, aspergiloid I (1), was isolated from the culture broth of Aspergillus sp. YXf3, an endophytic fungus derived from Ginkgo biloba. Its structure was unambiguously established by analysis of HRMS–ESI and spectroscopic data, and the absolute configuration was determined by low-temperature (100 K) single crystal X-ray diffraction with Cu Kα radiation. This compound is structurally characterized by a new carbon skeleton with an unprecedented 6/5/6 tricyclic ring system bearing an α,β-unsaturated spirolactone moiety in ring B, and represents a new subclass of norditerpenoid, the skeleton of which is named aspergilane. The hypothetical biosynthetic pathway for 1 was also proposed. The cytotoxic, antimicrobial, anti-oxidant and enzyme inhibitory activities of 1 were evaluated.

ChemInform Abstract: MODEL STUDY FOR SYNTHESIS OF THE CYTOCHALASIN D CYCLOUNDECANONE RING SYSTEM

1983 ◽  
Vol 14 (11) ◽  
Author(s):  
E. VEDEJS ◽  
M. J. ARNOST ◽  
J. M. EUSTACHE ◽  
G. A. KRAFFT
Keyword(s):  
Ring System ◽  
Cytochalasin D ◽  
Abstract Model ◽  
Model Study

scholarly journals The conversion of cephalosporins to 7 α-methoxycephalosporins by cell-free extracts of Streptomyces clavuligerus

1980 ◽  
Vol 186 (2) ◽  
pp. 613-616 ◽  
Author(s):  
J O'Sullivan ◽  
E P Abraham
Keyword(s):  
Methoxy Group ◽  
Biosynthetic Pathway ◽  
Streptomyces Clavuligerus ◽  
Ring System ◽  
Reducing Agent ◽  
Cephalosporin C ◽  
Methoxy Derivative

In the presence of S-adenosylmethionine, 2-oxoglutarate, Fe2+ and a reducing agent, cell-free extracts of Streptomyces clavuligerus convert cephalosporin C and O-carbamoyldeacetylcephalosporin C into 7 alpha-methoxy derivatives. No synthesis of a 7 alpha-methoxy derivative of deacetylcephalosporin C was detected in the system used, and the 7 alpha-methoxy derivative of deacetoxycephalosporin C was produced only in relatively small amounts. It appears that the 7 alpha-methoxy group is introduced after the cephalosporin ring system has been formed and that its introduction may represent the final step in a biosynthetic pathway.

Model study for synthesis of the cytochalasin D cycloundecanone ring system

1982 ◽  
Vol 47 (22) ◽  
pp. 4384-4386 ◽  
Author(s):  
E. Vedejs ◽  
M. J. Arnost ◽  
J. M. Eustache ◽  
G. A. Krafft
Keyword(s):  
Ring System ◽  
Cytochalasin D ◽  
Model Study

Synthetic Study on Lactonamycins, Part 2: Stereoselective Access to ABCD-Ring System

Synlett ◽  
2020 ◽  
Vol 31 (16) ◽  
pp. 1623-1628
Author(s):  
Keisuke Suzuki ◽  
Hiroshi Takikawa ◽  
Kazuki Murata ◽  
Shogo Sato ◽  
Takuma Kawada ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Hydroxy Group ◽  
Ring Opening ◽  
Ring System ◽  
Model Study ◽  
Viable Approach

Toward a stereoselective total synthesis of the lactonamycins, we recently reported an approach to the DEF-ring system. Here we report a model study for constructing the ABCD-ring system, revealing a viable approach through (1) construction of the C-ring by asymmetric benzoin cyclization, (2) introduction of an angular hydroxy group through oxidation of an isoxazolium salt, and (3) construction of the AB rings through a ring-opening/closing sequence.

Isolation, evaluation of bioactivity and structure determination of amethinol A, a prototypic amethane diterpene from Isodon amethystoides bearing a six/five/seven-membered carbon-ring system

2018 ◽  
Vol 74 (5) ◽  
pp. 635-640 ◽  
Author(s):  
Chen-Liang Zhao ◽  
Md. Shahid Sarwar ◽  
Jiang-Hai Ye ◽  
Chuen Fai Ku ◽  
Wan-Fei Li ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Structure Determination ◽  
Biosynthetic Pathway ◽  
Biological Activities ◽  
Ring System ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Hydroxy Groups ◽  
Close Contacts

We report the isolation of a novel diterpene, designated as `amethane', from Isodon amethystoides (Lamiaceae). The diterpene [amethinol A; systematic name: (4aR,4bR,7R,10aS)-4b,7-dihydroxy-7-isopropyl-1,1-dimethyl-9-oxododecahydrobenzo[a]azulene-4a(2H)-carboxylic acid], possesses a unique skeleton containing a six/five/seven-membered tricyclic system. Intermolecular O—H...O close contacts were found to the carboxyl, carbonyl and hydroxy groups, connecting molecules into a two-dimensional structure. A possible biosynthetic pathway has been proposed. In addition, the compound was evaluated for its biological activities against different disease targets, and was found to significantly attenuate RORγt-dependent autoimmune responses.

scholarly journals A Sesquiterpene Isonitrile with a New Tricyclic Skeleton from the Indo-Pacific Nudibranch Phyllidiella pustulosa: Spectroscopic and Computational Studies

2020 ◽  
Vol 73 (3) ◽  
pp. 129
Author(s):  
Desmond C.-M. Sim ◽  
Natasha L. Hungerford ◽  
Elizabeth H. Krenske ◽  
Gregory K. Pierens ◽  
Katherine T. Andrews ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Molecular Modelling ◽  
Density Functional ◽  
Biosynthetic Pathway ◽  
Antimalarial Activity ◽  
Computational Study ◽  
Ring System ◽  
Computational Studies ◽  
Molecular Modelling Studies ◽  
Modelling Studies

The sesquiterpene isonitrile, 9-isocyanoneoallopupukeanane 1, has been obtained from the Indo-Pacific nudibranch Phyllidiella pustulosa. The structure of 1, which was investigated by extensive NMR experiments, molecular modelling studies, and density functional calculations, has a different arrangement of the tricyclic ring system compared with other isonitrile metabolites isolated from nudibranchs or sponges. The viability of a biosynthetic pathway leading to 1, proposed to involve a series of carbocation rearrangements, is explored in a computational study. Isonitrile 1 exhibited micromolar antimalarial activity when screened against Plasmodium falciparum infected erythrocytes.

Synthetic Study on Acremoxanthone A, Part 2: Model Study on the EFG Xanthone Moiety through a Nitrile Oxide Cycloaddition–SNAr Sequence

Synlett ◽  
2020 ◽  
Author(s):  
Keisuke Suzuki ◽  
Hiroshi Nakakohara ◽  
Yoichi Hirano ◽  
Ken Ohmori ◽  
Hiroshi Takikawa
Keyword(s):  
Total Synthesis ◽  
Ring System ◽  
Nitrile Oxide ◽  
Dipolar Cycloaddition ◽  
Model Study ◽  
Snar Reaction ◽  
F Ring ◽  
Key Steps

AbstractToward a total synthesis of acremoxanthone A, we report a model study on the construction of the EFG ring system. The key steps include (1) an intermolecular 1,3-dipolar cycloaddition of an aryl nitrile oxide with a dienone, and (2) an SNAr reaction for construction of the F ring.

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