Ethyl (1R∗,3aS∗,7aS∗)-Octahydro-7a-methyl-7-oxo-1H-indene-1-acetate Using Tandem Reactions

The title compound was prepared in 29.5% overall yield using a five-step sequence involving two tandem reactions. The current work supports the earlier finding that a strong thermodynamic preference exists for an all-cis relationship across the three contiguous stereocenters at C(1), C(3a), and C(7a).     

Synthesis of stereospecifically labeled carbohydrates: Preparation of (3S)− and (3R)-[3-2H1]ascarylose

The general problem of the synthesis of 3,6-dideoxy sugars containing stereospecifically labeled hydrogen isotope at C-3 is addressed for the specific case of ascarylose (3,6-dideoxy-L-arabino-hexose).     

Synthesis of (1′S*,2R*,3R*)- and (1′S*,2R*,3S*)-N-arylsulfonyl-2-(1′-halogenethyl)-3-methylindolines and their selective toxicity against SH-SY5Y cell line

N-tosyl-2- and N-tosyl-4-halogen-substituted derivatives of 2-(1-methylbut-2-en-1-yl)aniline were synthesized and their molecular iodine-mediated cyclization was investigated. The cyclization upon interaction of N-tosyl-6-methyl-2-(1-methylbut-2-en-1-yl)aniline with molecular iodine in methyl tert-butyl ether or acetonitrile was studied, as well as the interaction of this sulfonamide with N-bromosucinimide in dichloromethane. Synthesized (2R*,3R*)- and (2R*,3S*)-N-arylsulfonyl-2-(1-halogenoethyl)-3-methylindoline derivatives showed cytotoxic activity against HEK293 cells, SH-SY5Y, Jurkat, and HepG2 cell lines. The compounds (2R*,3S*)-N-arylsulfonyl-7-bromo-2-(1-halogenoethyl)-3-methylindoline cis- 4a , stereoisomeric (2R*,3R*)-trans- 4h and (2R*,3S*)-N-tosyl-7-chloro-2-(1-halogenoethyl)-3-methylindoline cis- 4h demonstrated selective toxicity against SH-SY5Y cell line (IC₅₀ ≈ 3 ÷ 5 μM), and did not affect HEK293, Jurkat, and HepG2 cells.     

Asymmetric Synthesis of (-)-(2R,3R,6S)-Irnigaine

Introduction　　Asarelativelynewmemberofnaturalalkaloidswith2 ,6 disubstituted 3 piperidinolskeleton ,irnigaine 1wasisolatedfromthetubersofArisarumVulgare (Araceae)in1995byMelhaouiandBode .1Itsstructureandrelativeconfigurationswereelucidatedby1HNMRstudiesandtheabsoluteconfigurationwasproposedonthebasisofitsopti calrotation .1Soonafterthen ,Meyerandhisco workersreportedthefirstsynthesisof (- ) (2R ,3R ,6S) irni gaineandtheconfigurationconfirmation .Althoughtheirsynthesisroutewasshortan…     

Synthesis and structural characterization of camphanates of (−)-(2S3S,3S) and (+)-(2S,3R)-4-Phenyl-3-bromo-2-butanol diastereoisomers

The X-ray crystal structures of (–)-syn-4-phenyl-3-bromo-2-butyl camphanate (I) and (+-anti-4-phenyl-3-bromo-2-butyl camphanate (II) have been determined. Thesyn diastereoisomer of bromohydrin has the (2S,3S) absolute configuration whereas theanti diastereoisomer has the (2S,3R) absolute configuration. The crystallized derivatives I and II have been obtained by the reaction of each stereoisomer of bromohydrin, synthesized by reduction with baker's yeast, with (1S)-camphanic chloride. Crystal data: (I) C₂₀H₂₅BrO₄:M _w: 409.32; orthorhombic,P2₁2₁2₁;a=11.245(3),b=12.086(1),c=14.512(4) å; Z=4; finalR=0.053 for 1819 observed reflections. (II) C₂₀H₂₅BrO₄;M _w=409.32; monoclinic, P2₁;a=11.352(1),b=6.378(1),c=14.255(2) å,=110.38(1);Z=2; finalR=0.045 for 1672 observed reflections.     

Synthesis of (3S,5R)-cis- and (3S,5S)-trans-3,5-Dimethylvalerolactones and Their Conversion to Biotransformation Products of (S)-5-Ethyl-5-(2′-pentyl)barbituric Acid

(R,S)-5-Ethyl-5-(2′-pentyl)barbituric acid (I)^1,2 is metabolized in vivo to give all four possible optical isomers of 5-ethyl-5-(3′-hydroxy-1′-methylbutyl)barbituric acid (II). ^3,4 From metabolism studies of pure (1′S)- I and (1′3)-I, Palmer and co-workers^4,5 were able to determine the relative amounts of each of the four isomers formed. These studies showed that (1′S)-I gave mainly one enantiomer of (1′S)-II, whereas (1′R)-I gave approximately equal amounts of both (1′R)-II enantiomers.     

Enantioselective preparation of (2R,3R)-(+)- and (2S,3S)-(−)-2,3-epoxy-2-methylbutanoic acids and some derivatives

(2R,3R)-(+)- and (2S,3S)-(−)-2,3-epoxy-2-methylbutanoic acids (epoxyangelic acids) were prepared from (Z)-2-methyl-2-butenoic acid using the Sharpless asymmetric epoxidation method in combination with the use of (−)- and (+)-menthol as chiral auxiliaries. Both substances, obtained in high enantiomeric excess, were characterized by spectroscopic and optical activity data. Their absolute configuration was determined by correlation with (R)-(+)-2-methyl-1,2-butanediol.     

Asymmetric synthesis of heteroorganic analogs of natural products 5. Synthesis of pure diastereomers and enantiomers of fluoro-substituted (2S,3R)- and (2R,3R)-β-phenylserines

A convenient method is proposed for the preparative synthesis of pure diastereomers and enantiomers of fluoro-substituted (2S,3R)- and (2R,3R)--phenylserines by the hydroxyalkylation of the Ni(II) — complex of the Schiff base of glycine with (S)-2-N-(N¹-benzylpropyl)aminobenzophenone using the corresponding fluoro-substituted benzaldehydes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya. No. 8, pp. 1906–1913, August, 1991.     

A Convenient Synthesis of (S)-2-Methyl and (2S)-2,3-Dimethyl Butyl Phenylsulfones from (S)-(-)-3-Methyl-γ-butyrolactone

Suitably functionalized alkylphenylsulfones have been used as building blocks for the synthesis of several modified side-chains steroids¹. We describe here the synthesis of (S)-2-methyl and (2S)-2,3-dimethyl butyl phenylsulfones (4a) and (6), which can be used for the construction of the side chain of a few marine sterols² or brassinosteroids³ as well.     

Synthesis of 1-[6-Fluoro-(2S)-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2- ethanediol and 1-[6-Fluoro-(2R)-3H,4H-dihydro-2H-2-chromenyl]- (1R)-1,2-ethanediol

Benzopyran compounds possess diverse pharmacological properties such as β-blockade, anticonvulsant and antimicrobial.[1,2] Our interest has been focused on the synthesis of 1-[6-Fluoro-2S]-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2-ethanediol (6) and 1-[6-fluoro-(2R)-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2-ethanediol (7) which are particularly convenient precursor to (S,R,R,R)-NE (8). 8 containing four asymmetrical carbon atoms was reported to be the most active isomer.[3] Chandrasekhar[4] has reported on the synthesis of 8. The key step to synthesize this compound is to obtain the chiral chromanone 6 and 7. 6 was accomplished in 8 steps by the Clasien rearrangement and a one-pot Sharpless asymmetric epoxidation, but the compound 7 was accomplished in 10 steps. Johannes[5] used Zr-catalytic kinetic resolution of allylic ethers and Mo-catalyzed chromene formation to synthesize 8 in 14 steps. However both of the methods request many synthetic steps and expensive reagents.     

Synthesis and Crystal Structure of Spiro[1-bromo(S)-4-(R)-hydroxy-5-oxa-6-oxo-bicyclo[3.1.0]hexane-2,2''''-(3''''-diethyl-α-(S)-4''''''''-Cl-benzyloxyphosphonyl-4''''-(1R,2S,5R)-menthyloxybutyrolactone)]

1 INTRODUCTION In recent years, phosphorus compounds havebeen playing an important role in the new “high-tech” areas including life science and industrial te-chnology[1, .At the same time, the asymmetric syn- 2]thesis of various natural compounds containing cyc-lopropane components and organophosphorus grouphas attracted much attention due to their special bio-logical functions and antibiological activities[3～5].Despite the great advances in these areas, no novelapproach to the efficien…     

Asymmetric Conjugate Addition of Alcohols to (R)-(-)-5-[(1R,2S,5R)-Menthyloxy]-2-(5H)-Furanone

(R)-(-y5-[(IR,2S,5R)-menthyloxy](1)isausefulchiralsynthonreadilypreparedonatWo-stepprocedure-l']FindingsoffuranoneringsexistingascomponentSofsomenaturalproductSI'laswellastheiractivereactivityl']havestimu1atedeXtensiveresearchofitSasymmetricreactionswhichincludeDiels-Alderreactions,l']l,3-dipo1arcycloadditions,['1Michaelauditionsl5]andconjugateedditionsofaminesl']andmercaPtans.g4:,::7f:7':theseadductsledtovariousmultifunctionalhomochiralbuildingblockssuchas2-alkyl-l,4-butanediols,I'l2-aI…     

One-pot Synthesis and Crystal Structure of （1S,2R,3S,4R,5S）-1-Phenyl-2,4-dibenzoyl-3,5-difurylhexanol

(1S,2R,3S,4R,5S)-1-Phenyl-2,4-dibenzoyl-3,5-difurylhexanol 1 was synthesized by one-pot reaction of hypnone and furfurol in alkali H2O/EtOH solution and structurally defined to contain a chair-formed aliphatic carbocycle, on which the bulky substituents occupy the equatorial positions.     

(1R,4S,5S)-6-环己基-4-[(1R,2S,5R)-5-甲基-2-异丙基环己氧基]-3-氧杂-6-氮杂双环[3.1.0]-2-己酮的合成及结构表征

环已胺与差向异构体5-[(1R,2S,5R)-5-甲基-2-异丙基环己氧基]-3-溴-2(5H)-呋喃酮发生不对称Mi-chael加成-分子内亲核取代反应,并经柱层析分离,得到一对手性氮杂环丙烷-丁内酯衍生物,其中的标题化合物为首次得到的新手性化合物,产率17%,其结构经IR、1H NMR、13C NMR和HRMS进行了表征。     

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(…     

Simultaneous LC–UV Determination of 5-Methyl-1-(3-fluorophenyl)-2-(1H)- pyridone and Its Two Metabolites in Rat Plasma

A simple, rapid, and reproducible isocratic reverse-phase HPLC method was developed to simultaneously determine AKF-PD and its two oxidized metabolites in rat plasma. 5-Carboxyl-1-phenyl-2-(1H)-pyridone and phenacetin were used as internal standards to ensure the precision and accuracy of the method. The analytes were separated on a C₁₈ reversed-phase column with methanol—phosphate buffer (20 mM, pH 2.5) as mobile phase. The limits of detection for AKF-PD and its two oxidized metabolites was 0.1 μg mL^?1. The method is applicable for the pharmacokinetic studies of AKF-PD and its metabolites in rats.     

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.     

Vibrational spectra and stable conformations of N-methylacetamide and (1S,5S,6R)-6-acetylamino-(5′-methoxyindolo[2,3-b])bicyclo[3.2.1]oct-2-ene

IR absorption and Raman spectra of N-methylacetamide and (1S,5S,6R)-6-acetylamino-(5′-methoxyindolo[2,3-b])bicyclo[3.2.1]oct-2-ene are investigated. Optimized structures and harmonic force fields of stable conformers of both compounds are obtained by means of MP2 and DFT (B3LYP) methods using the 6-31+G** basis set. Based on quantum mechanical calculations, a detailed interpretation of spectra is proposed and vibrational frequencies of the most stable conformations are assigned. Correlations between structures and the spectra of N-methylacetamide and (1S,5S,6R)-6-acetylamino-(5′-methoxyindolo[2,3-b])bicyclo[3.2.1]oct-2-ene were considered and analytical spectral regions were proposed.     

Synthesis of (22R,23R,24S)-24-Methyl-5α-cholestane-3β,6α,22,23-tetraol, a Biosynthetic Precursor of Brassinolide

A biosynthetic precursor of brassinolide, (22R,23R,24S)-24-methyl-3-cholestane-3,6,22,23-tetraol was synthesized from ^{2 3}-22-keto steroid which was obtained from the corresponding 20-carbonitrile oxide. The side chain was built up by a series of successive transformations: hydride reduction of the initial enone, epoxidation of the allyl-like alcohol, and copper(I) cyanide-catalyzed opening of the 23,24-epoxy ring. The cyclic fragment was completed by opening of the cyclopropane ring with subsequent hydroboration and oxidation of the ⁵-bond.     

Separation and Determination of Cobalt, Rhodium,Nickel and Iridium with 2-(6-Methyl-2-Benzothiazolylazo)-5-Diethylamino Phenol by HPLC

The synthesis and spectrophotometric properties of 2-(6-methyl-2-benzothiazolylazo)-5-diethylamino phenol (MBTAE), and the use of it as a precolumn derivatizing reagent to separate Co(Ⅱ), Ni(Ⅱ), Rh(Ⅲ) and Ir( Ⅳ) complexes by HPLC are discussed. When the mobile phase consists of methanol/water(90/10 Ⅴ/Ⅴ), acetate buffer with pH 4. 0 and 5×10-5 mol/L EDTA solution, the four complexes Can be separated within 9 min on ODS column. The detection limits (20 μL sample size) are 0. 059 ppb, 0. 062 ppb, 0. 053 ppb and 0. 049 ppb for Co(Ⅱ) , Rh(Ⅲ), Ni(Ⅱ) and lr(Ⅳ) respectively at a signal-to-noise ratio of 3.