Enantioselective synthesis of γ-lactones from thioglycolic acid: Syntheses of (−)-muricatacin and 5-epi-(−)-muricatacin

An approach for the enantioselective synthesis of functionalized γ-lactones and its application to the syntheses of (−)-muricatacin 1a and 5-epi-(−)-muricatacin 1b is reported. A sequential oxidation of the intermediate 4 with m-chloroperoxybenzoic acid was conducted to realize the reaction mechanism.     

Stereospecific Synthesis of (−)-β-Turmerone and (−)-Bisacurol

The structure of (+)-β-turmerone ((+)- 1a ), a constituent of the rhizomes of Curcuma longa Linn. , and Curcuma xanthorriza, is established as (1′R,6S)-2-methyl-6-(4′-methylenecyclohex-2′-en-1′-yl)hept-2-en-4-one by synthesis of its enantiomer (−)- 1a , and of the corresponding (1′S,6S)-diastereoisomer (+)- 1b as well. In a stereospecific seventeen-step procedure, the monoterpene diols 2a and 2b of well-established configuration are converted into the target compounds (−)- 1a and (+)- 1b , respectively. Moreover, (−)-bisacurol (−)- 3a (II), the enantiomer of another bisabolane sesquiterpene derived from Curcuma xanthorriza, is obtained as a single stereoisomer and shown to be (1′S,6R)-2-methyl-6-(4′-methylenecyclohex-2′-en-1′-yl)hept-2-en-4-ol, the relative configuration at the remaining OH-substituted chiral center C(4) still being unknown.     

Synthesis of (S)-(−)-β-cuparenone and (S)-(−)-cuparene

A short and efficient synthesis of the title compounds is described. (S)-(−)-β-Cuparenone was prepared in 31% yield from p-tolualdehyde and mesityl oxide in eight steps. Absolute stereochemistry was established by means of a diastereoselective cyclopropanation using (R,R)-hydrobenzoin as a recoverable auxiliary.     

5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇的合成

以5-雄烯二醇为原料,用微生物转化的方法合成了两个重要的神经甾体5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇。所用菌种总枝毛霉为我们自己筛选,并首次应用于5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇的合成中。     

A convenient chiron approach to (4R,5R)-5-hydroxyalkylbutan-4-olides and the corresponding 7-oxa analogues from d-(+)-mannitol via an advanced common precursor: syntheses of (−)-muricatacin, 7-oxa-(−)-muricatacin, (4R,5R)-(−)-5-hydroxy-4-decanolide,and (4R,5R)-(−)-7-oxa-5-hydroxy-4-dodecanolide

An efficient and concise chiron approach toward the synthesis of (−)-muricatacin and its unnatural 7-oxa analogue starting from commercially available and inexpensive d-(+)-mannitol via an advanced common chiral precursor has been described. In addition, (4R,5R)-(−)-5-hydroxy-4-decanolide and (4R,5R)-(−)-7-oxa-5-hydroxy-4-dodecanolide were also synthesized to show the versatility of this synthetic strategy. The methodology involves the conversion of a common chiral intermediate, prepared from d-(+)-mannitol in six steps, to a variety of target molecules in only two steps.     

Total Synthesis of (R)-(−)-β-Cuparenone

Abstract

(R)-(?)-β-Cuparenone has been synthesized from (S)-(+)-acid-2 obtained via resolution of the racemic acid. Two of the noteworthy steps are (a) repeated methylation of ester (+)-8 with LDA/MeI to furnish (+)-10 and (b) the reaction of 12, having two neopentyl units with NaCN.     

Scaleable processes for the synthesis of (−)-β-d-2,6-diaminopurine dioxolane (Amdoxovir,DAPD) and (−)-β-d-2-aminopurine dioxolane (APD)

An efficient and scalable synthesis of (?)-DAPD and (?)-APD has been developed. We discovered that t-butyl cyanoacetate can be used as a new additive for the sugar nucleoside base coupling step en route to DAPD with improved β-selectivity and an isolated yield four-fold greater than the original process scale method. Using this new process, (?)-DAPD has been prepared on greater than 20 g scale. In the synthesis of (?)-APD, a key enzyme-catalyzed hydrolysis reaction afforded the water soluble deprotected α-anomer while leaving the β-anomer completely untouched.     

Strukturelle Abwandlungen an N-Acetylneuraminsäure, 25. Mitt.: Synthese von Methyl-2-α-glycosiden von 4-epi-, 7-epi-, 8-epi- und 7,8-bis-epi-N-Acetylneuraminsäure

The -methylketoside of N-acetylneuraminic acid methylester (4) is transformed via the deacetylated compound5 into the 9,8-O-isopropylidenderivative6 which could be oxidized regioselectively by RuO₄ to the corresponding 4-oxo-sialic acid analogue7. Reduction with the boraneammonia complex produces a 1:1 mixture of6 and the desired -methylketoside of 9,8-O-isopropyliden-4-epi-N-acetyl-neuraminic acid methylester (8). Removing of the isopropylidene group gives the -methylketoside of 4-epi-N-acetylneuraminic acid methylester (9), which was further transformed to the ammonium salt of 4-epi-N-acetylneuraminic acid -methylketoside (10). On the other hand compound5 was turned into the 4,8,9-tri-O-t-butyldimethylsilylderivative11 a from which the corresponding 7-oxo-compound12 by oxidation with RuO₄ derives. The reduction of12 with BH₃ - NH₃ yielded a 1:1 mixture of the starting material11 a and the desired 7-epi-derivative13 a which gives either via the purified peracetylated -methylketosid of 7-epi-N-acetylneuraminic acid methylester (14) or a direct saponification the sodium salt of 7-epi-N-acetylneuraminic acid--methylketoside (15).Applying the Königs-Knorr procedure to the peracetylated 8-epi-N-acetylneuraminic acid methylester (16) gives rise to the formation of a 1:1 mixture of the corresponding - and -methylketosides17 and18 besides traces of the corresponding 2,3-dideoxy-2,3-dideohydro-sialic acid derivative19. After chromatographic separation of17 further saponification leads to the sodium salt of 8-epi-N-acetylneuraminic acid--methylketoside (20). In an analogous procedure the sodium salt of 7,8-di-epi-N-acetylneuraminic acid--methylketoside (25) was prepared starting from the peracetylated 7,8-di-epi-N-acetylneuraminic acid methylester (21), whereby a mixture of the - and -methylketosides22 and23 was formed in a ratio 95:5 besides traces of the peracetylated 2,3-dideoxy-2,3-didehydrosialic acid methylester (24).

On study leave from the Department of Chemistry, Postgraduate and Research Center, R.B.N.B. College, Shrirampur-413709 (MS), India     

Asymmetric Reduction of Acetophenone with (−)-β-chlorodiisopinocampheylborane, and Derivatization with (−)-Menthyl Chloroformate. An Undergraduate Organic Synthesis, GC Analysis, and Molecular Modeling Project

Molecular vibration plays an important role in chemistry, both in chemical reactions and in the characterization and measurement of molecular structure and bonding. Normal modes provide the conceptual framework for understanding molecular vibrations. For example, the analysis of infrared spectra, an important tool for chemists, relies heavily on the concept of normal modes; yet, undergraduate students, even chemistry majors, seldom gain a thorough understanding of normal modes through the traditional chemistry curriculum. In fact, the most commonly used physical chemistry textbooks give only a cursory introduction to this concept, leaving out the substantive development. This occurs presumably because normal modes emerge from a multistepped mathematical analysis of the molecular dynamics. While the mathematical skill needed for each step typically has been covered in an introductory calculus course, the full development is a lengthy process and skipped in the texts. Thus, students have little opportunity to develop a sound conceptual understanding of vibrational modes and fundamental vibrational frequencies, even though they inevitably encounter these terms in their future work.     

Synthesis of (4R,5S)-(−)- and (4S,5S)-(+)-L-Factors and Muricatacin from D-Glucose

Abstract

In connection with our projects on the synthesis of biologically active 5-hydroxyalkan-4-olides which have a chiral 2.3-diol unit,¹ we have carried out the synthesis of (4R,5S)-(?)- and (4R,5S)-(+)-L-factors (1).² the proposed autoregulators from Streptomyees griseus, and muricatacin (2),³ a biologically active constituent from the seeds of Annona muricata L. via 2.3-dihydroxy aldehydes derived from D-glucose. Hex-3-enofuranose4 was prepared by the elimination of thetriflate derived from D-glucose.     

24-亚甲基-胆甾烷-3β,5α,6β-三醇的合成

豆甾醇;24-亚甲基-胆甾烷-3β;5α;6β-三醇的合成     

Expedient syntheses of indolizidines (−)-167B and (−)-209D

Indolizidine alkaloids (−)-167B and (−)-209D were synthesized via an expedient route using hydroacylation and amination.     

3α-氨基-2β,17β-二羟基-16β-哌啶基-5α-雄甾烷和2β-氨基-3α,17β-二羟基-16β-哌啶基-5α-雄甾烷的合成

本文报道了3α-氨基-2β,17β-二羟基-16β-哌啶基-5α-雄甾烷和2β-氨基-3α,17β-二羟基-16β-哌啶基-5α-雄甾烷的合成方法。     

3α-氨基-2β,17β-二羟基-16β-哌啶基-5α-雄甾烷和2β-氨基-3α,17β-二羟基-16β-哌啶基-5α-雄甾烷的合成

1975年Varg ftig等发现,3α-氨基-2β-羟基-5α-雄甾-17-酮盐酸盐(Org 6001)具有抗心律失常作用,它不仅口服有效,疗效优于利多卡因,而且无激素活性,被认为是一类新型结构的抗心律失常药。以后,人们又对Org 6001进行了一系列的结构改造工作,但     

简便高效合成15β,16β-亚甲基-雄甾-5-烯-3β-醇-17-酮

采用对甲苯磺酸(pTsOH)和i氟乙酸(TFA)为催化剂,邻碘酰苯甲酸(IBX)为氧化剂,于40-45℃,在T01.DMSO混合溶剂中,将醋酸去氢表雄酮选择性脱氢,简便高效地制备了3β-乙酰氧基.雄甾-5.15-二烯-17-酮(I),产率分别为77%和89%.本合成线路有效避免了经溴代脱溴和发酵等合成线路反应繁多、试剂毒性大、成本高以及单纯IBX选择性脱氢反应温度高、反应时间长等不足.然后将化合物I在碱性条件下水解得到3β-羟基.雄甾-5,15-二烯-17-酮(Ⅱ),产率92%.最后将化合物Ⅱ与碘化三甲基氧化锍进行迈克尔共轭加成制得目的物15β,16β-亚甲基.雄甾-5-烯-3β-醇-17-酮(Ⅲ),产率89%.中间体和目的物经紫外光谱、红外光谱、核磁共振氧谱、质谱及元素分析确证了其化学结构.     

16,17α-环氧-5α-和5β-孕甾-3β-醇-20-酮和16,17α-环氧-16β-甲基-5α-⊿9(11)-孕甾烯-3β-醇-20-酮的微生物脱氢

16,17α-环氧-5α-和5β-孕甾-3β-醇-20-酮(1,2)用诺卡氏菌脱氢分别得到4,5,6,7和8,5,6,7四个化合物,其中16,17α-环氧-⊿⁴-孕甾烯-3,20-双酮(5)是主要产物.1和2分别用节杆菌脱氢时则均得到两个20α-羟基的不饱和化合物15和16,其中⊿^1,4-双酮16是主要产物.16,17α-环氧-16β-甲基-5α-⊿⁹⁽¹¹⁾-孕甾烯-3β-醇-20-酮(3)用诺卡氏菌脱氢可得到12,13,14三个化合物,其中16,17α-环氧-16β-甲基_-⊿^4,9(11)-孕甾二烯-3,20-双酮(13)是主要产物.综上所述,5α和5β甾族化合物用诺卡氏菌脱氢主要脱去C_4,5两个氢原子形成⊿⁴-烯-3-酮化合物,而采用节杆菌可使C_l,2和C₄,5位同时脱氢形成⊿^1,4-双烯-3-酮化合物.     

3β-乙酰氧基-5β,6β-环氧-6α-甲基-25-D螺甾与三氟化硼的反应

3β-乙酰氧基-5β,6β-环氧-6α-甲基-25D螺甾(Ⅲ)在与三氟化硼反应时按双竪鍵破环規律生成5α-氟-6β-羟基-6α-甲基化合物(Ⅳ),产物經变为已知体(Ⅴ)証明其結构与构型。     

A Novel Synthesis of (-)-10-epi-α-Cyperone

The eudesmane derivative, (-)-10-epi-α-cyperone 1, is widely used as a chiral starting material for the synthesis of other fused-ring sesquiterpenes1. The first synthetic work was reported by Howe and co-workers via condensation of (+)-dihydrocarvone 2 with 1-diethylaminopentan-3-one methiodide in 32% yield2. Previously, our group reported the synthesis of compound 1 by treating ketone 2 with ethyl vinyl ketone (EVK) directly under different conditions1a, but the yields were not satisfacto…     

Synthesis of ( )-5α-Hydroxy-β-selinene and (-)-5β-Hydroxy-β-selinene

Eudesmanederivativeshavebeendrawingconsiderableattentionduetotheirwidespectrumofbiologicalproperties,particularlyantifeedant,cellgroWthinhibitoryandplantgroWthregulatingactivitiesl'2.Recently,twoepimericeudesmanederivatives( )-5a-hydroxy-6-selinene1and(-)-56-hydroxy-6-selinene2wereisolated3fromtheaerialpartsofCSubtraPicaFMell.,andtheirstructuresweredeterminedbyspectroscopicmethods.Herein,wereportafacilesynthesisofbothtwodiastereomers1and2from( )-dihydrocarvone3infivesteps,usingtheregioselect…     

3β-乙酰氧基-7β-羟基-17,17-亚乙二氧基-15β,16β-亚甲基雄甾-5-烯的合成

以3β-乙酰氧基-15β,16β-亚甲基雄甾-5-烯-17-酮为原料,用化学氧化法,经3步合成标题化合物,其结构经IR,MS表征,总收率50．8％。