Concise Formal Synthesis of (S)-Gregatin B

Matsuo, Keizo; Kanayama, Masaru; Xu, Jin; Takeuchi, Rie; Nishiwaki, Koichi; Asaka, Yukihiro

doi:10.3987/com-05-10391

Cited by 10 publications

(16 citation statements)

References 17 publications

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“…Figure 2). A formal total synthesis of (+)‐gregatin B followed in 2005 16. It appeared to corroborate the 3D structure.…”

Section: A Structurally Deceptively Simple Class Of Natural Productsmentioning

confidence: 72%

“… Revised9 (“second‐generation”) structures of the natural products from Figure 1 [absolute configurations, if any, derived from purported total15 and formal syntheses16 of (+)‐gregatin B ( 1 ); otherwise same as in first‐generation structures]. Additionally: originally published (“first‐generation”) structures of cyclogregatin [(+)‐ 7 12], penicilliol A [(+)‐ 8 13], and penicilliol B [(+)‐ 9 13].…”

Section: A Structurally Deceptively Simple Class Of Natural Productsmentioning

confidence: 99%

“…The constitution ( 1b ) and the absolute configuration [( S )] of (+)‐gregatin B had seemingly been established by purported total syntheses of both racemic 1b 22,15 and (+)‐( S )‐ 1b 15 by Takaiwa and Yamashita. This endeavor is summarized in Scheme jointly with what seemed to be a formal total synthesis of (+)‐( S )‐ 1b 16. The starting materials were the lactone‐containing carboxylic acid ( S )‐ 27 31 and D ‐lactic acid, respectively.…”

Section: Analysis Of Former Structural Assignment Errorsmentioning

confidence: 99%

“…The considerable spread of the specific rotations of these compounds is disconcerting. Ref 16. speculates whether ( S )‐ 38 → ( S )‐ 39 was accompanied by a “partial racemization”.…”

Section: Analysis Of Former Structural Assignment Errorsmentioning

confidence: 99%

See 3 more Smart Citations

Total Syntheses of the Gregatins A–D and Aspertetronin A: Structure Revisions of These Compounds and of Aspertetronin B, Together with Plausible Structure Revisions of Gregatin E, Cyclogregatin, Graminin A, the Penicilliols A and B, and the Huaspenones A and B

Burghart-Stoll

Brückner

2012

Eur J Org Chem

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Comprehensive comparisons of 1H and 13C NMR chemical shift values in the furanone cores a, b, and c provide plausible support for a reassessment of the furanone nuclei of the title compounds from b to c. Total syntheses via enantiomerically pure lactic esters were based on the Seebach–Fráter “self‐reproduction of stereocenters” methodology. Attachment of the hexadienyl side‐chain in a trans,trans‐selective manner was achieved by addition of the Seebach–Fráter enolate to trans‐hex‐4‐en‐1‐al rather than to trans‐hex‐3‐en‐1‐al. The type‐c furanone cores of the synthetic materials were reached by single or double acylation of a model γ‐hydroxy‐β‐oxo ester (compound 50) and its hexadiene‐containing counterpart 29. Our syntheses confirmed the novel connectivities in six compounds. In addition, they required revision of the configuration of a quaternary carbon atom in five cases. Moreover, they allowed elucidation of the configurations of four previously unassigned stereocenters. Hindsight analyses of why the furanone cores of the title compounds had been misinterpreted as a and/or b instead of c are given. Why the stereocenters in the heterocycles had been incorrectly configured, on the bases (a) of relay studies in the 1960s, and (b) of a 1984 total synthesis of gregatin B, is also discussed.

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“…Figure 2). A formal total synthesis of (+)‐gregatin B followed in 2005 16. It appeared to corroborate the 3D structure.…”

Section: A Structurally Deceptively Simple Class Of Natural Productsmentioning

confidence: 72%

Section: A Structurally Deceptively Simple Class Of Natural Productsmentioning

confidence: 99%

Section: Analysis Of Former Structural Assignment Errorsmentioning

confidence: 99%

Section: Analysis Of Former Structural Assignment Errorsmentioning

confidence: 99%

See 2 more Smart Citations

Total Syntheses of the Gregatins A–D and Aspertetronin A: Structure Revisions of These Compounds and of Aspertetronin B, Together with Plausible Structure Revisions of Gregatin E, Cyclogregatin, Graminin A, the Penicilliols A and B, and the Huaspenones A and B

Burghart-Stoll

Brückner

2012

Eur J Org Chem

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“…Additionally, three olefinic H-atom signals (d(H) 7.18, 6.59, and 6.06) were observed. Nine C-atom signals corresponding to two sp 2 quaternary C-atoms, four CH, one CH 2 , and two Me groups were detected in the The furan-3(2H)-one derivatives constitute a group of polyketides produced by fungi [14] [17] [19] [25], and they show a wide range of bioactivities, such as phytotoxic [25] [26] and DNA polymerase [19] inhibitory activities. Though many furan-3(2H)one derivatives have been characterized in nature, to the best of our knowledge, this is the first report on N-bearing furanone derivatives.…”

mentioning

confidence: 99%

N‐Bearing Furanone Derivatives from an Endophytic Fungus in Huperzia serrata

Xiang

Shan

Liang

et al. 2013

Helvetica Chimica Acta

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Two new polyketide derivatives, huaspenones C and D (1 and 2, resp.), were isolated from the cultures of an endophytic fungus Peyronellaea sp. HS-12, derived from the stems of Huperzia serrata. They share N-bearing furan-3(2H)-one backbone, and 2 has an unprecedented furo[3,2-c]pyridine skeleton. Their structures including the absolute configuration were elucidated by extensive spectroscopic analysis combined with quantum-chemical calculations. (2E,4E)-6-hydroxy-2-methylocta-2,4dienoic acid (3), a key intermediate of the biosynthesis of 1 and 2, was also obtained from the endophyte.Introduction. -Endophytic fungi are microorganisms which spend their life cycle, as a whole or partly, colonizing inter-and/or intra-cellularly inside the healthy tissues of their host plant, typically causing no apparent symptoms of disease [1]. The research on endophytes showed that they are potential sources of novel biologically active secondary metabolites for exploitation in medicine, agriculture, and industry [2 -5]. Furthermore, results from many researches indicated that they could metabolize the same substance as their own host plants [6 -8], rendering them an alternative source of plant secondary metabolites.Huperzia serrata, a Chinese folk medicinal herb, is well-known for the discovery of hupzine A, a potent, highly specific, and reversible inhibitor of acetylcholinesterase [9] [10]. In a previous study, two new furan-3(2H)-one derivatives, huaspenones A and B (4 and 5, resp.), were isolated from Aspergillus sp. XW-12 derived from the stems of H. serrata [11] 1 ). In this work, two novel N-containing furan-3(2H)-one derivatives, 1 and 2, were isolated from the rice culture of an endophytic fungus Peyronellaea sp. HS-12 obtained from the stems of H. serrata, together with a key intermediate of the biosynthesis of 1 and 2, i.e., (2E,4E)-6-hydroxy-2-methylocta-2,4-dienoic acid (3). In addition, two known compounds, andrastin A (4) [13] and huaspenone B (5) [11], were also obtained from the endophytic fungus. Their structures were elucidated by NMR spectroscopy, especially 2D-NMR spectra. The absolute configurations of 1 and 2 were determined by CD analysis, combined with quantum-chemical calculation. To the best of our knowledge, huaspenones C and D (1 and 2, resp.) are the first examples of Nbearing furan-3(2H)-one derivatives in nature, and 2 has an unprecedented furo[3,2c]pyridine skeleton.

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