An efficient and simple synthesis of (−)-wine lactone

A, short and efficient diastereoselective synthesis of (−)-wine lactone (−)-4a involving FeCl₃/NaI-mediated iodolactonization of γ,δ-unsaturated acid 7 as the key step is described.     

An efficient and practical asymmetric synthesis of (−)-tasimelteon

Tasimelteon is a useful drug for the treatment of Non-24 in totally blind individuals. An efficient and convenient asymmetric synthesis of tasimelteon has been developed from 4-vinyl-2,3-dihydrobenzofuran through six steps in 53% overall yield using the Corey–Bakshi–Shibata (CBS0 asymmetric reduction of ketone as a key step.     

An efficient synthesis of (R)-(−)-baclofen

In this report we describe an efficient synthesis of (R)-(−)-baclofen, a selective GABA_B agonist used as an antispastic agent. Our strategy is based on an enantioselective deprotonation of a cyclobutanone easily obtained by [2+2] cycloaddition of 4-chlorostyrene and dichloroketene.     

An efficient and facile synthesis of N-Cbz-β-aminoalkanesulfonamides

An efficient method for the synthesis of N-Cbz-β-aminoalkanesulfonamides was described.N-Cbz-β-aminoalkanesulfonamides were readily prepared in good yields from a variety of amino alcohols,including optically active ones,via N-Cbz protection with benzyl chloroformate,Mitsunobu esterification reaction with thiolacetic acid,N-chlorosuccinimide oxidation,and ammonolysis process.     

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.     

An efficient synthesis of enantiopure (+)- and (−)-3-exo-amino-7,7-dimethoxynorbornan-2-exo-ols

We describe the synthesis of new amino alcohols (+)- and (−)-3-exo-amino-7,7-dimethoxynorbonan-2-exo-ols. The (+)- or (−)-7,7-dimethoxy-1,4,5,6-tetrachlorobicyclo[2.2.1]hept-5-en-2-endo-ol, obtained from the enzyme catalysed transesterification of the racemate, was reduced and dechlorinated (Na/NH₃; ethanol), followed by pyridinium chlorochromate oxidation of the resultant alcohols to the corresponding ketones. After treatment with t-BuOK/BuONO, in a nitrosation reaction, α-keto oximes were obtained. Reduction over two steps with NaBH₄ and NaBH₄/NiCl₂·6H₂O followed by in situ acetylation furnished the corresponding acetamido esters, which were hydrolysed with CH₃OH/Na to produce the enantiopure amino alcohols in good yields.     

A simple and efficient stereoselective synthesis of (−)-cleistenolide

A simple and straightforward stereoselective synthesis of α,β-unsaturated δ-lactone, (?)-cleistenolide has been accomplished in 10 steps in an overall yield of 19%, starting from inexpensive and commercially available starting materials, respectively. This linear synthesis utilizes Sharpless asymmetric dihydroxylation, sulfur ylide mediated epoxide opening followed by ring-closing metathesis (RCM) for the formation of six-membered lactone ring as the key step sequence.     

A stereocontrolled synthesis of (−)-detoxinine from l-ascorbic acid

A stereoselective synthesis of (−)-detoxinine, the core unit of the detoxifying agent detoxin D₁, is presented. The approach, characterized by the use of an inexpensive starting material and by the easy and stereoselective preparation of the key 4,5-disubstituted oxazolidin-2-one 11, proves to be a suitable alternative to the known procedures.     

Total Syntheses of (−)-Secologanin, (−)-5-Carboxystrictosidine,and (−)-Rubenine

The first enantioselective total syntheses of (−)-secologanin ( 1 ), (−)-5-carboxystrictosidine ( 2 ), and (−)-rubenine ( 3 ) were accomplished in 10, 9, and 14 steps, respectively. The key transformation in the synthesis of 1 was a sequential anti-selective organocatalytic Michael reaction/Fukuyama reduction/spontaneous cyclization to form an optically active dihydropyran ring. In addition, the secologanin tetraacetate ( 16 ), which is a potential key intermediate for the bioinspired divergent syntheses of monoterpenoid indole alkaloids, was prepared in gram-scale in seven steps. The total syntheses of 2 and 3 , which are classified as glycosylated monoterpenoid indole alkaloids, were achieved through bioinspired transformations such as a diastereoselective Pictet–Spengler reaction, a site- and stereoselective epoxidation, and a site-selective epoxide ring-opening followed by a lactonization reaction.     

An expeditious,highly efficient,catalyst and solvent-free synthesis of 9,10-dihydro-anthracene-9,10-α,β-succiniimide derivatives

Abstract

A simple, fast, and highly efficient protocol has been developed for the synthesis of 9,10-dihydro-anthracene-9,10-α,β-succinic imide derivatives by simple mixing and grinding of 9,10-dihydro-anthracene-9,10-α,β-succinic anhydride with various aliphatic, aromatic amines, and hydrazines. This catalyst and solvent-free green approach provided the condensation products within few minutes at room temperature in quantitative yield.     

An expeditious formal synthesis of (−)-epibatidine

A short route to (−)-epibatidine is described. It includes a hetero-Diels–Alder reaction of a chiral non-racemic acyl-nitroso derivative and 2-t-butyldimethylsilyloxycyclohexadiene followed by chemical manipulations to furnish a known precursor of the natural product in 11% overall yield.     

Enantiodivergent synthesis of (+)- and (−)-isolaurepan

The enantiodivergent synthesis of (+)-and (?)-isolaurepan was achieved from a common chiral template easily available from tri-O-acetyl-d-glucal, using as key step a diastereoselective thermal Claisen rearrangement, combined with a ring expansion reaction using trimethylsilyldiazomethane.     

A novel and efficient synthesis of (+)- and (−)-trans-2-aminocyclohexanol by enzymatic hydrolysis

Both enantiomers of trans-2-aminocyclohexanol were obtained by enzymatic hydrolysis of (±)-2-azidocyclohexanoates using lipases and subsequent hydrogenation.     

Total synthesis of (−) verbenalol and (−) epiverbenalol

The first asymmetric synthesis of (−) verbenalol and (−) epiverbenalol, starting from the organometallic complex (−) 1, is described.     

An efficient and facile procedure for synthesis of octyl polyglucoside

Nonionic surfactant alkyl polyglucoside (APG) was prepared by direct glycosidation of alkyl alcohol with glucose in the presence of sulfate acid-silica gel (H_2SO_4/SiO_2) as solid acidic catalyst.The quantity of catalyst was only of 1 wt%,based on the glucose,and the conversion of glucose was close to 100% at 110℃in 1.5h.The product was characterized by FT-IR,mass and ~1H NMR spectra.The degree of polymerization (DP) of the glucose in the product was 1.37,and critical micelle concentration (CMC) of product was only 0.0104 wt%.     

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.     

An efficient method for the synthesis of enantiopure cis-α,β-epoxy acids

Enantiopure cis-α,β-epoxy acids were prepared via a modified Darzen's reaction employing the titanium-mediated bromination–aldolization of chiral acetate thioimide enolate.     

The synthesis of (−)-cis- and (−)-trans-crobarbatic acid

The synthesis of both cis- and trans-crobarbatic acid is reported. The five-step sequence proceeds in high yield and with control of both relative and absolute stereochemistry. The key step in the synthesis is the Birch reductive alkylation of a chiral furoic acid which sets the absolute stereochemistry of the products. The stereochemistry of the compounds described was proven unambiguously by X-ray crystallography on one synthetic intermediate and on trans-crobarbatic acid.     

An efficient dehyrohalogenation method for the synthesis of α,β,β-trifluorostyrenes, α-chloro-β,β-difluorostyrenes and E-1-arylperfluoroalkenes

Dehydrofluorination of 1-aryl-1,2,2,2-tetrafluoroethanes (ArCHFCF₃) and 1-aryl-1-chloro-2,2,2-trifluoroethane (ArCHClCF₃) using lithiumhexamethyldisilazide (LHMDS) in tetrahydrofuran (THF) at room temperature produced 1,2,2-trifluorostyrene and 1-chloro-2,2-difluorostyrene, respectively, in very good isolated yields. Dehydrofluorination of 1,2,2,3,3,3-hexafluoro-1-phenyl-propane (PhCHFCF₂CF₃) and 1,2,2,3,3,4,4,4-octafluoro-1-phenyl-butane (PhCHFCF₂CF₂CF₃) using LHMDS produced the corresponding substituted olefins (1-phenyl-1,2,3,3,3-pentafluoroprop-1-ene and 1-phenyl-1,2,3,3,4,4,4-pentafluorobut-1-ene) in good yield and high E-selectivity. Dehydrofluorination of 1-chloro-1-phenyl-2,2,3,3,3-pentafluoropropane (PhCHClCF₂CF₃) and 1-chloro-1-phenyl-2,2,3,3,4,4,4-heptafluorobutane (PhCHClCF₂CF₂CF₃) produced a mixture of the corresponding E and Z olefins (PhCClCFCF₃ and PhCClCFCF₂CF₃) in good yield.