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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/07/15 08:30:14」(JST)

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Semisynthesis or partial chemical synthesis is a type of chemical synthesis that uses compounds isolated from natural sources (e.g. plant material or bacterial or cell cultures) as starting materials. These natural biomolecules are usually large and complex molecules. This is opposed to a total synthesis where large molecules are synthesized from a stepwise combination of small and cheap (usually petrochemical) building blocks.

Semisynthesis is usually used when the precursor molecule is too structurally complex, too costly or too inefficient to be produced by total synthesis. From a synthesis viewpoint, life is an amazing chemical factory, and for some chemical products, it is hard to compete with life as a synthetic route—sometimes a lowly plant can grow for pennies' worth of amortized farming investment what total synthesis would struggle expensively to produce. Thus humanity collaborates with nature to make the most of this remarkable cost-effectiveness.

Drugs derived from natural sources are usually produced by harvesting the natural source or through semisynthetic methods: one example is the semisynthesis of LSD from ergotamine, which is isolated from ergot fungus cultures. The commercial production of paclitaxel is also based on semisynthesis (see: paclitaxel total synthesis).

The antimalarial drug artemether (a component of Coartem) is a semisynthetic derived from naturally occurring artemisinin. The latter is unstable due to the presence of a lactone group and therefore this group is replaced by an acetal through organic reduction with potassium borohydride and methoxylation:^[1]

References

^ An Improved Manufacturing Process for the Antimalaria Drug Coartem. Part IMatthias Boehm, Peter C. Fuenfschilling, Matthias Krieger, Ernst Kuesters, and Fritz Struber Org. Process Res. Dev.; 2007; 11(3) pp 336 - 340; (Article) doi:10.1021/op0602425

English Journal

Phytochemistry To Medicinal Chemistry: Isolation, Semisynthesis, Evaluation And Computational Studies.

Singla RK, Varadaraj Bhat G, Diaz HG1.
Current topics in medicinal chemistry.Curr Top Med Chem.2014 Mar 24. [Epub ahead of print]
PMID 24660677

A convenient semisynthesis of myricetin-3-O-β-d-glucuronide.

Wu HL1, Tong YF, Wu S.Author information 1a State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Key Laboratory of Biosynthesis of Natural Products, Ministry of Health of PRC, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing 100050 , China.AbstractMyricetin-3-O-β-d-glucuronide, a bioactive flavonol glycoside, was synthesized effectively starting from myricetrin in a total yield of 49.2%. The structures of all synthetic compounds were confirmed by 1H, 13C NMR, and HR-MS techniques.
Journal of Asian natural products research.J Asian Nat Prod Res.2014 Mar 11. [Epub ahead of print]
Myricetin-3-O-β-d-glucuronide, a bioactive flavonol glycoside, was synthesized effectively starting from myricetrin in a total yield of 49.2%. The structures of all synthetic compounds were confirmed by 1H, 13C NMR, and HR-MS techniques.
PMID 24611744

One-Step Semisynthesis of Oleacein and the Determination as a 5-Lipoxygenase Inhibitor.

Vougogiannopoulou K1, Lemus C, Halabalaki M, Pergola C, Werz O, Smith AB 3rd, Michel S, Skaltsounis L, Deguin B.Author information 1Division of Pharmacognosy and Natural Products Chemistry, Department of Pharmacy, University of Athens , Panepistimiopolis, GR-15771, Athens, Greece.AbstractThe dialdehydes oleacein (2) and oleocanthal (4) are closely related to oleuropein (1) and ligstroside (3), the two latter compounds being abundant iridoids of Olea europaea. By exploiting oleuropein isolated from the plant leaf extract, an efficient procedure has been developed for a one-step semisynthesis of oleacein under Krapcho decarbomethoxylation conditions. Highlighted is the fact that 5-lipoxygenase is a direct target for oleacein with an inhibitory potential (IC50: 2 μM) more potent than oleocanthal (4) and oleuropein (1). This enzyme catalyzes the initial steps in the biosynthesis of pro-inflammatory leukotrienes. Taken together, the methodology presented here offers an alternative solution to isolation or total synthesis for the procurement of oleacein, thus facilitating the further development as a potential anti-inflammatory agent.
Journal of natural products.J Nat Prod.2014 Feb 25. [Epub ahead of print]
The dialdehydes oleacein (2) and oleocanthal (4) are closely related to oleuropein (1) and ligstroside (3), the two latter compounds being abundant iridoids of Olea europaea. By exploiting oleuropein isolated from the plant leaf extract, an efficient procedure has been developed for a one-step semis
PMID 24568174

Japanese Journal

NATURAL-PRODUCT-BASED INSECTICIDAL AGENTS 16 : SEMISYNTHESIS OF C7-OXIME SULFONATE ESTER DERIVATIVES OF OBACUNONE AS INSECTICIDAL AGENTS AGAINST MYTHIMNA SEPARATA WALKER (Dedicated to Professor Isao Kuwajima on the occasion of his 77th birthday)

Yu Xiang,Ding Guodong,Gao Zhinan [他]
Heterocycles : an international journal for reviews and communications in heterocyclic chemistry 90(2), 1367-1374, 2015-01-01
NAID 40020330733

天然物ビスデメトキシクルクミンのイソキサゾールおよびピラゾール誘導体の合成と殺ダニ活性

LUO Jinxiang,DING Wei,ZHANG Yongqiang [他],Yang Zhenguo,Li Yang,Ding Lijuan
Journal of Pesticide Science 38(4), 214-219, 2013
Sixteen isoxazole and pyrazole derivatives of bisdemethoxycurcumin (BDMC) modified in β-diketone were synthesized, and their structures were confirmed by IR, 1H NMR, 13C NMR, MS and elemental analysis …
NAID 130004939730

日本産イチイ科植物内生菌のタキソイド生成能の検討

石野貴久,寺田珠実,鮫島正浩 [他],鴨田重裕
東京大学農学部演習林報告 -(126), 45-58, 2012-02
… Several methods have been developed for taxol production, e.g, total chemical synthesis, semisynthesis from precursor Baccatin III and plant cell culture. …
NAID 120005330783