- A general asymmetric route to enantio-enriched isoflavanes via an organocatalytic annulation of o-quinone methides and aldehydes
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Reported herein is a general approach to optically active isoflavanes based on a chiral amine-catalyzed [4 + 2] asymmetric annulation of o-quinone methides and aldehydes. A number of naturally occurring isoflavanes, including equol, sativan, isosativan, v
- Zhang, Jian,Zhang, Shuangzhan,Yang, Huixin,Zhou, Ding,Yu, Xueting,Wang, Wei,Xie, Hexin
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p. 2407 - 2411
(2018/05/24)
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- Unified total syntheses of (-)-medicarpin, (-)-sophoracarpan a, and (±)-kushecarpin a with some structural revisions
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The total syntheses of medicarpin, sophoracarpan A, and kushecarpin A from a common intermediate are achieved by using ortho- and para-quinone methide chemistry. Additionally, the relative stereochemistry of sophoracarpan A and B have been reassigned.
- Feng, Zhen-Gao,Bai, Wen-Ju,Pettus, Thomas R. R.
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p. 1864 - 1867
(2015/02/19)
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- Synthesis, optical resolution, absolute configuration, and osteogenic activity of cis-pterocarpans
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A convenient synthesis of natural and synthetic pterocarpans was achieved in three steps. Optical resolution of the respective enantiomers was accomplished by analytical and semi-preparative HPLC on a chiral stationary phase. For medicarpin and its synthetic derivative 9-demethoxymedicarpin, the absolute configuration was confirmed by a combination of experimental LC-ECD coupling and quantum-chemical ECD calculations. (-)-Medicarpin and (-)-9-demethoxymedicarpin are both 6aR,11aR-configured, and consequently the corresponding enantiomers, (+)-medicarpin and (+)-9-demethoxymedicarpin, possess the 6aS,11aS-configuration. A comparative mechanism study for osteogenic (bone forming) activity of medicarpin (racemic versus enantiomerically pure material) revealed that (+)-(6aS,11aS)-medicarpin (6a) significantly increased the bone morphogenetic protein-2 (BMP2) expression and the level of the bone-specific transcription factor Runx-2 mRNA, while the effect was opposite for the other enantiomer, (-)-(6aR,11aR)-medicarpin (6a), and for the racemate, (±)-medicarpin, the combined effect of both the enantiomers on transcription levels was observed. The Royal Society of Chemistry 2012.
- Goel, Atul,Kumar, Amit,Hemberger, Yasmin,Raghuvanshi, Ashutosh,Jeet, Ram,Tiwari, Govind,Knauer, Michael,Kureel, Jyoti,Singh, Anuj K.,Gautam, Abnish,Trivedi, Ritu,Singh, Divya,Bringmann, Gerhard
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p. 9583 - 9592
(2013/01/16)
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- Catalytic specificity of pea O-methyltransferases suggests gene duplication for (+)-pisatin biosynthesis
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S-adenosyl-l-methionine: 2-hydroxyisoflavanone 4′-O-methyltransferase (HI4′OMT) methylates 2,7, 4′-trihydroxyisoflavanone to produce formononetin, an essential intermediate in the synthesis of isoflavonoids with methoxy or methylenedioxy groups at carbon 4′ (isoflavone numbering). HI4′OMT is highly similar (83% amino acid identity) to (+)-6a-hydroxymaackiain 3-O-methyltransferase (HMM), which catalyzes the last step of (+)-pisatin biosynthesis in pea. Pea contains two linked copies of HMM with 96% amino acid identity. In this report, the catalytic activities of the licorice HI4′OMT protein and of extracts of Escherichia coli containing the pea HMM1 or HMM2 protein are compared on 2,7,4′-trihydroxyisoflavanone and enantiomers of 6a-hydroxymaackiain. All these enzymes produced radiolabelled 2,7-dihydroxy-4′-methoxyisoflavanone or (+)-pisatin from 2,7,4′-trihydroxyisoflavanone or (+)-6a-hydroxymaakiain when incubated with [methyl-14C]-S-adenosyl-l-methionine. No product was detected when (-)-6a-hydroxymaackiain was used as the substrate. HI4′OMT and HMM1 showed efficiencies (relative Vmax/Km) for the methylation of 2,7,4′-trihydroxyisoflavanone 20 and 4 times higher than for the methylation of (+)-6a-hydroxymaackiain, respectively. In contrast, HMM2 had a higher Vmax and lower Km on (+)-6a-hydroxymaackiain, and had a 67-fold higher efficiency for the methylation of (+)-6a-hydroxymaackiain than that for 2,7,4′-trihydroxyisoflavanone. Among the 15 sites at which HMM1 and HMM2 have different amino acid residues, 11 of the residues in HMM1 are the same as found in HI4′OMTs from three plant species. Modeling of the HMM proteins identified three or four putative active site residues responsible for their different substrate preferences. It is proposed that HMM1 is the pea HI4′OMT and that HMM2 evolved by the duplication of a gene encoding a general biosynthetic enzyme (HI4′OMT).
- Akashi, Tomoyoshi,VanEtten, Hans D.,Sawada, Yuji,Wasmann, Catherine C.,Uchiyama, Hiroshi,Ayabe, Shin-ichi
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p. 2525 - 2530
(2007/10/03)
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