Preparation of (1R∗,2S∗,5R∗,6R∗)-1-Methyl-2,5,6-Tribromo-Cyclooctane and 3-Methyl-6,7-Dibromocyclooctene

Abstract

Reaction of 4,5-dibromobicyclo[6.1.0]non-4-ene with anhydrous AlBr₃ forms (1R?,2S?,5R?,6R?)-1-methyl-2,5,6-tribromocyclooctane and 3-methyl-6,7-dibromocyclooctene.

     

Asymmetric synthesis of (−)-(1R,7aS)-absouline

The most efficient and concise asymmetric synthesis of (?)-(1R,7aS)-absouline to date, which was accomplished in eight steps and 20% overall yield from commercially available starting materials, is described. The doubly diastereoselective conjugate addition of lithium (S)-N-benzyl-N-(α-methylbenzyl)-amide to an enantiopure α,β-unsaturated ester derived from l-proline was employed as the key step. Subsequent hydrogenolytic N-debenzylation and acid-promoted cyclisation of the resultant β-amino ester produced the 1-aminopyrrolizidin-3-one scaffold, then reduction with DIBAL-H was followed by DCC-mediated coupling with (E)-p-methoxycinnamic acid to complete the synthesis of (?)-(1R,7aS)-absouline.     

Versatile methodology for the synthesis and α-functionalization of (2R,3aS,7aS)-octahydroindole-2-carboxylic acid

An improved strategy for the effective synthesis of enantiomerically pure (2R,3aS,7aS)-octahydroindole-2-carboxylic acid (Oic), based on the formation of a trichloromethyloxazolidinone derivative, has been developed. Additionally, the completely diastereoselective α-alkylation of such oxazolidinone provides a very convenient and concise route to enantiopure α-tetrasubstituted derivatives of this Oic stereoisomer.     

3-((1R,3aS,3aS,10aR)-十氢-(1H,4H)-吡啶并[1,6]萘啶-1-基)丙-1-胺的合成

以廉价易得的苦参碱为起始原料,经过开环、酯化反应、水解等步骤,得到4-((3aS,3aS,10aR)-2-(叔丁氧基羰基)十氢-(1H,4H)-吡啶并[1,6]萘啶-1-基)丁酸(5)。5再经过Curtius重排反应,得到叔丁基(1R,3aS,3aS,10aR)-1-(3-(((苄氧基)羰基)氨基)丙基)八氢-(1H,4H)-吡啶并[1,6]萘啶-2(3H)-羧酸叔丁酯(6)。然后,6脱去Cbz基团得到(1R,3aS,3aS,10aR)-1-(3-氨基丙基)八氢-(1H,4H)-吡啶并[1,6]二氮杂萘-2(3H)-羧酸叔丁酯(7),最后,7脱去Boc基团成功得到苦参碱衍生物的重要中间体3-((1R,3aS,3aS,10aR)-十氢-(1H,4H)-吡啶并[1,6]萘啶-1-基)丙-1-胺(8),总收率28%。目标化合物和中间体的结构经¹H NMR, ¹³C NMR和HR-MS确证。      

An Efficient Synthesis of Ethyl 7-Chloro-6-fluoro-l-methyl-4-oxo-1, 4-dihydro-[1, 3]thiazeto[3, 2-a]quinoline-3-carboxylate as Intermediate of the Prulifloxacin Containing Tricyclic Fluoroquinolone

Novel ethyl 7-chloro-6-fluoro-l-methyl-4-oxo-1, 4-dihydro-[1, 3]thiazeto[3, 2-a]quino- line-3-carboxylate 2 was prepared from 3-chloro-4-fluoroaniline in eight steps. It can be used as a new intermediate for the synthesis of tricyclic fluoroquinolones.     

Oxiranyl β-Aminovinyl Ketones. 7. Synthesis of 5-Hydroxy-3-(1-oxo-2,3-epoxyalkyl)benzofurans

5-Hydroxy-3-(1-oxo-2,3-epoxyalkyl)benzofurans were obtained with yields of up to 81% by the reaction of p-benzoquinone with oxiranyl -dimethylaminovinyl ketones in acetic acid.     

A New Approach to the Construction of Pyrrolizidine and Indolizidine Skeleton: Enantioselective Synthesis of (1S, 7aS)-1-hydroxypyrrolizidine and (1S, 8aS)-1-hydroxyindolizidine

Pyrrolizidineandindolizidineareconunonstructura1elementsofmanynaturallyoccurringalkaloidsfoundinplantsandmicroorganisms.Thediverseandpotentbiologicalactivitiesofthesealkaloidshavedrawnmuchattentioninthestudiesoftheirpharmacologyandpreparation'.Ingeneral,mostconventionalsyntheticmethodologiesinvolvedthefinalformationofoneortwoC-Nbondsofpyrrolizidineandindolizidineskeleton'.andtheseresultedintheinefficientprotectinggroupchemistry,especiallywithrespecttohandlingtheaminoresidueTherefore.themostef…     

An Efficient Synthesis of Ethyl 7-Chloro-6-fluoro-1-methyl-4-oxo-1,4-dihydro-[1, 3]thiazeto[3, 2-a]quinoline-3-carboxylate as Intermediate of the Prulifloxacin Containing Tricyclic Fluoroquinolone

The fluoroquinolones such as ciprofloxacin and sparfloxacin have been widely used for the treatment of various bacterial infections1. Their mechanism of action is believed to be associated with inhibition of bacterial DNA gyrase2. Moreover, recent studies…     

Molecular conformation of the racemic indan derivative (±)-1-trans-3-(3,4-dichlorophenyl)-2,3-dihydro-1H-indene-1-carboxamide

This paper presents the structural characterization of the indan derivative (±)-1-trans-3-(3,4-dichlorophenyl)-2,3-dihydro-1H-indene-1-carboxamide, which was unambiguously determined by X-ray diffraction (XRD) to be a racemate (R/S: 50/50) crystallizing in an achiral crystal structure (P2₁/c, a = 9.3180(1) Å, b = 7.9070(2) Å, c = 19.7550(4) Å, β = 103.250(1)°, V = 1416.75(5) Å³ and Z = 4). The diastereomers are related by the inversion symmetry and linked by H bond forming a dimer. The crystal packing is stabilized by hydrogen bonds, including the classical one responsible for the formation of centrosymmetric dimers, and non-classical ones involving C–H···O and C–H···π-aryl interactions. The intra and intermolecular geometry of the title compound is compared to the (±)-1-trans-3-(3,4-dichlorophenyl)-2,3-dihydro-1H-indene-1-carboxylic acid one, which also present an achiral crystal structure from racemates (R/S: 50/50). The two indan derivatives crystallize in a very similar unit cell.     

Synthesis of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)-octahydroquinolin-7-ones

A synthesis of the enamine (−)-(1′S)-5-ethyl-1-(1′-phenylethyl)-1,2,3,4-tetrahydropyridine 4 and its application in a synthesis of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)-octahydroquinolin-7-ones 5 and 6 is described. In addition, an X-ray study of 6 is reported. Finally, the preparation of (+)-(4aS,8aR)-4a-ethyl-octahydroquinolin-7-one 7 is described.     

Synthesis of 24-Methylene-cholest-5-ene-7-oxo-3β,19-diacetate

24-Methylenecholest-5-ene-7-oxo-3β,19-diacetate 5 was synthesized starting from stigmasterol via twelve step reactions in 4.1% overall yield. It can be served as a key intermediate for the synthesis of 24-methylenecholest-5-ene-3β,7β,19-mol 1, a naturally occuring polyhydroxylated sterol with potential biological activity.     

Facile Synthesis of Dibenzo-7λ(3)-phosphanorbornadiene Derivatives Using Magnesium Anthracene

Unprotected dibenzo-7λ(3)-phosphanorbornadiene derivatives RPA (A = C(14)H(10) or anthracene; R = (t)Bu, dbabh = NA, HMDS = (Me(3)Si)(2)N, (i)Pr(2)N) are synthesized by treatment of the corresponding phosphorus dichloride RPCl(2) with MgA·3THF, in cold THF (～20% to 30% isolated yields). Anthracene and the corresponding cyclic phosphane (RP)(n) form as coproducts. Characteristic NMR features of the RPA derivatives include a doublet near 4 ppm in their (1)H NMR spectra and a triplet peak in the 175-212 ppm region of the (31)P NMR spectrum ((2)J(PH) ～14 Hz). The X-ray structures of the AN-PA and (HMDS)PA derivatives are discussed. Thermolysis of RPA benzene-d(6) solutions leads to anthracene extrusion. This process has a unimolecular kinetic profile for the (i)Pr(2)NPA derivative. The 7-phosphanorbornene anti-(i)Pr(2)NP(C(6)H(8)) could be synthesized (70% isolated yield) by thermolysis of (i)Pr(2)NPA in 1,3-cyclohexadiene.     

N,N′-bis(1-ferrocenyl-1-oxo-3-methyl)propenylethylenediamine and its metal complexes

Summary A new Schiff base ligand, N,N-bis(l-ferrocenyl-1-oxo-3-methyl)propenylethylenediamine (H₂L) and its copper(II), zinc(II), cobalt(II), nickel(II), cadmium(II) and manganese(II) complexes have been prepared, and the structure of the copper complex has been determined by single crystal X-ray techniques and refined to R = 0.041 for 7403 independent reflections. The copper atom is situated in a distorted planar environment. The dihedral angle between planes of two chelating rings which do not contain the metal is 33.5°. Two substituted Cp rings are conjugated with two chelating acacim rings. The iron-centroid forms an angle of 179.4°. The Cp rings are twisted from the eclipsed conformation.     

Synthesis and Crystal Structure of Ethyl 2,7,7-Trimethyl-4-(4''''-methylphenyl)- 5-oxo-1,4,5,6,7,8-hexahydroquinoline-3- carboxylate in Aqueous Medium

1 INTRODUCTION The 1,4-dihydropyridines (1,4-DHPs) are biologi- cally interesting compounds and have been developed extensively in pharmacology. 1,4-DHP derivatives are used therapeutically in the treatment of cardio- vascular disorders, especially hypertension and coro- nary heart disease such as angina pectoris, atheros- clerosis, etc. The DHPs have emerged as one of the most important classes of drugs for the treatment of gastrointestinal disease, Raynaud?s disease, pulmonary hyper…     

Synthesis of the Polymer of 1 {3-O[(R)-1 (L-Alanyl-D-Isoglutamyl Carbonyl) Ethyl]-α-D-Glucopyranos-6-O-Carbonycarbonyl}Ethylene

Abstract

The polymer of 1- 3-O [(R)1-(L-alanyl-D-isoglutamyl carbonyl)ethyl] α-D-glucopyranos-6-O-carbonyl ethylene was synthesized as a acryloyl type polymer by fixing the D-glucose analog (GADP) of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), which is the minimum required structure responsible for the immunoadjuvant activity of bacterial cell-wall peptidoglycan. N- [2-(1,2-O-Isopropylidene-6-O-acryloyl-α-D-glucofuranos-3-Oyl)-(R)-propionyl] -L-alanyl-D-isoglutamine benzyl ester (6) was prepared as a key monomer in the synthesis. The homopolymerization of 6 and the copolymerization of 6 with hydrophobic acryloyl monomers were carried out in benzene at 60°C by using 2,2′-azobisisobutyronitrile as a radical initiator to give homopolymer 7 and copolymer 10, respectively. Removal of isopropylidene and benzyl protecting groups from 7, 10 and 8, 11 was carried out by acid treatment with trifluoroacetic acid/water (6:1 v/v) and by catalytic hydrogenolysis with palladium carbon, respectively, to afford the homopolymer 9 and the copolymer 12.     

β-Lactam Ring Opening in the Reformatsky Reaction of (3R,4R)-4-Acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)azetidin-2-one with Ethyl 4-Bromo-3-oxopentanoate

Russian Journal of Organic Chemistry - The Reformatsky reaction of (3R,4R)-4-acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)­azetidin-2-one with ethyl 4-bromo-3-oxopentanoate gave...     

Unexpected retro-Michael reaction of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1-phenylethyl)octahydroquinolin-7-ones

An unexpected retro-Michael reaction of (−)-(1′S,4aS,8aR)-and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1′-phenylethyl)octahydroquinolin-7-ones 1 and 2 is described. In addition, a diastereospecific intramolecular Michael reaction of 3·HCl and 4·HCl is reported.     

The Reactions of 1-Acetothiosemicarbazidc with P(NR_2)_3 PC1_3 and PCI_5

A Series of new heterocyciophosphorus compounds were synthesizec oy cyclocondensa-tion of 1-acetothiosemicarbazide with P(NR2)3. The further reaction of these compounds with P(NR2)3 gave different compounds depending upon different reaction conditions. The 1-acetothiosemicarbazide can also condense with PCl3 and PCl5 similarly, The reaction mechanism, the spectral properties and chemical properties of these products were also studied and discussed.     

A Convenient Method for Synthesis of Novel Cyclic Ethers (1R,2R,3R,5S,7S,9R,12R)-3-(t-Butyldimethylsilyl)oxy-7-methoxymethyl-oxy-2,10-dimethyl-12-oxatricyclo [7.2.1.0~(5,12)] dodecane

Coloradocin, a novel macrolide antibiotic from cultures of Actinoplanes coloradoensis1exhibits activity against pathogenic anaerobic and microaerophilic species2. Because itslow toxicity and substantial oral activity3, , as well as its unusual structure5, several 4research groups initiated approaches towards the synthesis of coloradocin6, whichculminated in the synthesis of 18-deoxynargenicin A1 by Kallmerten et al.7. …     

(2S,3aR,7aS)-八氢-1H-吲哚-2-甲酸苄酯的合成

通过合成路线的改进以及合成工艺的优化,方便高效地得到了抗高血压药物群多普利的关键中间体(2S,3aR,7aS)-八氢-1H-吲哚-2-甲酸苄酯.产品结构及绝对构型通过NMR及HPLC进行表征,与文献报道的数据完全一致.最终以99%的对映选择性及13.2%的产率得到目标化合物.为群多普利关键中间体的合成提供了一条可工业化的途径.