Synthesis of (24R)-homobrassinolide

The synthesis from stigmasterol of C-29 brassinosteroids containing an (R)-ethyl group at C24 — (24R)-homocastasterone and (24R)-homobrassinolide — is described. The structure of the carbon skeleton of the side-chain was achieved by condensing a C-22 aldehyde with the appropriate sulfoneInstitute of Organic Chemistry, Belarus Academy of Sciences, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 385–391, May–June, 1994.     

Synthesis of (22S, 23S)-homobrassinolide and brassinolide from stigmasterol

(22S, 23S)-Homobrassinolide (2α, 3α, 22S, 23S-tetrahydroxy-24S-etyl-B-homo-7-oxa-5α-cholestan-6-one) and brassinolide (2α, 3α 22R, 23R-tetrahydroxy-24S-methyl-B-homo-7-oxa-5α-cholestan-6-one) were synthesized from stigmasterol and shown to promote plant growth.     

Synthesis and biological evaluation of 3-beta,20(R)-dihydroxy-protost-24-ene

The possible lanosterol precursor, 3β, 20(R)-dihydroxy-protost-24-ene ( 1 a ) has been prepared, in thirteen steps, from 3α-hydroxy-4α, 8, 14-trimethyl-18-nor-5α, 8α, 9β, 13ξ, 14β-androstan-17-one (mixture of 2 and 3 ). In vitro experiments with rat liver homogenates failed to convert 1 a to lanosterol.     

Synthesis of (22E,24R)-5a-ergosta-2,7,22-trien-6-one

The synthesis of the 5a-hydroxy-2,7,22-trien-6-one (3) has been achieved by the mesylation of ergosterol (1a) and oxidation of the resulting mesylate (1b) with chronic acid to 3,5a-dihydroxy-7,22-dien-6-one 3-mesylate, followed by elimination.Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, 220141, Minsk, ul. Akad. Kuprevicha. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 100–102, January–February, 1999.     

Stereoselective Synthesis of Phosphorus Analogs of (R)-Carnitine and (R)-Gabob

Bioreduction of 3-substituted-2-oxoalkanephosphonates by baker's yeast afforded corresponding 2-hydroxy-alkanephosphonates in good yields and ee value. These compounds ( 2a,b ) could serve as useful chirons for the stereoselective synthesis of phosphorus analogs of (R)-Carnitine and (R)-GABOB.     

Synthesis of （S） and （R）-tilisolol hydrochloride

Tilisolol hydrochloride 1,a non-selectiveβ-adrenoceptor blocker,was developed as a drug for the treatment of hypertension and angina pectoris.The optical active forms of 1,1a and 1b were synthesized from inexpensive phthalic anhydride 2 in eight steps with 13%(S) and 15%(R) overall yield.     

Asymmetric Synthesis of (R)-and (S)-Moprolol

A simple and effective procedure for the enantioselective synthesis of (R)-and (S)-moprolol was described.The key step was the asymmetric synthesis of enantiopure (R)-and (S)-guaifenesin,which were synthesized from enantioenriched (R)-3-chloro-1,2-propanediol and (S)-epichlorohydrin via kinetics of hydrolysis resolution of racemic epichlorohydrin by chiral Salen-CoIIII complex.The e.e.values of both the optical compounds were above 98%,and the chemical structures of the target compounds were confirmed by 1H NMR,13C NMR,IR,and MS.     

Synthesis of (+)-(R)-Tiruchanduramine

The absolute stereochemistry of the marine alkaloid (+)-(R)-tiruchanduramine was established via a convergent total synthesis in six steps and 15.5% overall yield from Fmoc-D-Dab(Boc)-OH.     

Expedient Synthesis of (R)-Patulolide A

An efficient derivation of the title compound has been formulated from easily accessible 10-undecenoic acid (1). Thus, dodec-11-en-2-ol (3), prepared from 1, was pyranylated and subjected to bromination with NBS followed by acetolysis to furnish (2E)-1-acetoxy-11-(tetrahydropyranyloxy)dodec-2-ene (5). Its hydrolysis, oxidation, and depyranylation afforded the (2E)-hydroxy ester (9). This, on Candida rugosa lipase-catalyzed acetylation, SeO(2) oxidation, hydrolysis, and Yamaguchi macrolactonization, led to (R)-patulolide A (I) with 67.1% ee. The enantiomeric excess was improved to 97% by first resolving the alcohol 3 via porcine pancreatic lipase catalyzed acetylation and converting the corresponding (R)-acetate (13) to I as done above.     

Total Synthesis of 3 (R)-Panaxynol

Panaxynol1,asacommonconstituentofmanyplantparts',wasfirstdescribedbyTakahashietal.2in1964asaconstituentofPanaxyginseng.C.A.MeyershowedinhisBioassayshowedthatpanaxynolhadselectiveinvitrocytotoxicityagainstL-1210',MKI,B-16,andL-929cancercelllinescomparedtonormalcellcultures4.TheabsoluteconfigurationhadbeenestablishedbyLarsenetal.5tobe3R.Hereinwereportthefirsttotalstereoselectivesynthesisofpanaxynol(l).C'-CIafragmentofpanaxynol1wasobtainedaccordingtothefollowingsequencefReagentsandconditio…     

Synthesis of (R,S)-muscone

Construction of the carbon-skeleton of (R,S)-muscone was achieved by reacting methyllithium with the dianion of cyclopentadecanedione-1,3, itself accessible by hydration of cyclopentadecanediyne-1,3.

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Synthese von (R,S)-Muscon (Kurze Mitteilung) Short communication

Zusammenfassung Die Konstruktion des Kohlenstoffgerüstes von (R,S)-Muscon gelingt durch Reaktion des Dianions von Cyclopentadecandion-1,3, das durch Hydratisierung von Cyclopentadecandiin mit Methyllithium erhältlich ist.

     

Synthesis of anti-Alzheimer (R)-arundic acid

The asymmetric synthesis of the anti-Alzheimer agent (R)-arundic acid has been performed via a diastereoselective photodeconjugation reaction as the key-step. The synthetic approach involves a readily available chiral auxiliary, diacetone-d-glucose, and allows access to either enantiomer as illustrated by the synthesis of (S)-arundic acid. Both enantiomers were obtained in 88% ee using the same chiral auxiliary.     

Synthesis of (R)-cyanohydrins by crude (R)-oxynitrilase-catalyzed reactions in micro-aqueous medium

In diisopropyl ether or ethyl acetate under micro-aqueous conditions, the enantioselective synthesis of (R)-cyanohydrins from aldehydes and methyl ketones was studied using crude (R)-oxynitrilase prepared from almonds. This reaction system performed well over the temperature range of 4°C to 30°C.     

Synthesis and Crystal Structure of 5（R）-（1R,2S,5R）-Menthoxy-4（R）- N-cyclohexylaminobutyrolactone

1INTRODUCTION Substitutedγ-butyrolactones are a group of impor-tant compounds containing unique carbon skeleton of butyrolactone which is widely present in many natural products and have received considerable interest because of their biological and medicinal properties[1～4].Therefore,much attention has been paid to the new asymmetric methods for synthesi-zing these interesting compounds[5～11].The prece-ding results led us to explore the possibility of using cyclohexylamine to convert5(…     

(1R,6R)-(+)-鱼腥藻毒素的合成

鱼腥藻毒素(Anatoxin-a)是自兰藻类水华鱼腥藻(Anabaena flos-aquae)中分离的一种氮杂双环胺类生物碱,其化学结构及绝对构型经X光晶体衍射法测定分析为:(1R,6R)(+)-2-乙酰基-9-氮双环[4.2.1]壬-2-烯,简称为AnTX-a。     

精确控制合成Au_(36)(SR)_(24)金原子簇

<正>金原子簇已经成为一种重要的金纳米材料,广泛地应用于纳米科学和纳米技术领域~1。由于量子尺寸效应,金原子簇具有独特的物理化学性质,使其在光学、太阳能光伏、催化以及生物学领域具有很好的前景~(2,3)。随着现代合成方法的发展,尺寸聚焦方法和配体交换方法成为金原子簇的主要合成方法~4。尺寸聚焦方法的关键点是从多分散的金聚     

Enantioselective Total Synthesis of (R,R)-Blumenol B and d9-(R,R)-Blumenol B

C₁₃-norisoprenoids are of particular importance to grapes and wines, as these molecules influence wine aroma and have been shown to significantly contribute to the distinct character of various wine varieties. Blumenol B is a putative precursor to a number of important wine aroma compounds, including the well-known compounds theaspirone and vitispirane. The enantioselective synthesis of (R,R)-blumenol B from commercially available 4-oxoisophorone was achieved using a short and easily scaleable route, which was then successfully applied to the synthesis of poly-deuterated d9-blumenol B.