A Convergent Route for the Synthesis of AF—5

AF-5 was synthesized through a convergent method. The key step was the Robinson annulation using a key intermediate pentyl vinyl ketone.     

Synthesis of 7‐Alkoxy/Hydroxy‐α‐methyltryptamines

Abstract

A simple method for the preparation of 7‐alkoxy/hydroxy‐α‐methyl‐DL‐tryptamines is reported. The key steps of the synthesis are the Japp–Klingemann coupling of 2‐piperidone‐3‐carboxylic acid 3 with diazonium salts 4, the Fischer‐type cyclization of hydrazones 5 to β‐carboline derivatives 6 and their hydrolysis to title compounds 8.     

Application of Dichlorovinyl Xyloside for the Novel Synthesis of 2,3,4‐Tri‐O‐methyl‐D‐xylono‐1,5‐lactone

A novel synthesis of 2,3,4‐tri‐O‐methyl‐D‐xylopyranose, 4, and its oxidation product 2,3,4‐tri‐O‐methyl‐D‐xylono‐1,5‐lactone, 5, are reported. The new synthesis applies a regioselective Wittig‐like reaction of tetra-O-acetyl-D-xylopyranase, 1, with triphenylphosphine and carbon tetrachloride to yield an O‐dichlorovinyl xyloside protected at C‐1, 2. The protecting group facilitates the permethylation of xylose and is removed under the methylation conditions, to yield tetra-O-acetyl-D-xylopyranase, 3. The anomeric methyl group was removed under mildly acidic conditions to give 2,3,4‐tri‐O‐methyl‐D‐xylopyranose, 4, in good yield. Compound 4 was oxidized using pyridinium chlorochromate to give the title compound, 5, in 95% yield.     

Acronycine Analog: New Selective Synthesis of 6‐Methoxy‐3,3‐dimethyl‐3H,7H‐pyrano[2,3‐c]xanthen‐7‐one

A new, convenient, and selective route to the dimethylpyrano[2,3‐c]xanthen‐7‐one, analog of acronycine, via aromatization and dehydrogenation reactions from the corresponding saturated hexahydro intermediate is described.     

Facile and Versatile Route to the Synthesis of Fused 2‐Pyridones: Useful Intermediates for Polycyclic Sytems

The reaction of various heteroaromatic amino nitriles with diethyl malonate under basic conditions is reported. This reaction affords a series of different highly functionalized 2‐pyridone condensed systems, which can be suitable intermediates in the construction of polyheterocyclic structures.     

A New Synthesis of 5,8‐Dimethyl‐2‐tetralone—A Potential Intermediate for the Synthesis of Ring‐A Aromatic Sesquiterpenes. Novel Transformation During Acetoxylation of 5,8‐Dimethyldihydronapthalene

Abstract

An efficient synthesis of 5,8‐dimethyl‐2‐tetralone 4 starting from 5,8‐dimethyl‐1‐tetralone 2 is described. It was converted into the unsaturated derivative 3, which on epoxidation followed by acid hydrolysis yielded tetralone 4. Acetoxylation of 3 with manganese(III) acetate and potassium bromide afforded dimethylnaphthalene 8 and derivative 9.     

Synthesis of 3‐Aryl‐5‐methyl 4‐Substituted [1,2,4]Triazoles

Treatment of N‐substituted acetamides with oxalyl chloride generates imidoyl chlorides, which react readily with aryl hydrazides. Following cyclization, triazoles can easily be obtained in moderate to good yields. 5‐Methyl triazoles can be further functionalized through α‐lithiation and subsequent reaction with an electrophile.     

Synthesis of Acylated Methyl 2‐Acetamido‐2‐Deoxy‐α‐D‐Mannopyranosides

Abstract

2‐Acetamido‐2‐deoxy‐β‐D‐mannopyranose (1) was glycosylated by the Fischer method using an acidic ion‐exchange resin as the catalyst to give α‐methyl glycoside 2. Selective pivaloylations of methyl 2‐acetamido‐2‐deoxy‐α‐D‐mannopyranoside (2) have been studied under various reaction conditions. Two partially pivaloylated products were submitted to additional acetylations. All structures were established by NMR spectroscopy. Structure of the methyl 2‐acetamido‐2‐deoxy‐3,6‐di‐O‐pivaloyl‐α‐D‐mannopyranoside (4) was determined by X‐ray analysis.     

Vapor—liquid equilibria of the binary mixtures methyl chloride — methanol and dimethyl ether — methyl chloride and of the ternary mixture dimethyl ether — methyl chloride — methanol

Vapor Liquid Equilibria in mixtures of dimethyl ether, methyl chloride and methanol were investigated in a static equilibrium apparatus for temperatures 250 K < T <350 K and pressures up to 1 MPa. Temperature, pressure and the composition of the liquid and the vapor phase were determined.The consistency of the binary experimental data was checked and parameters of several g^E-models were fitted. The binary parameters were used to predict the ternary VLE and the calculated results were compared with the experimental data.     

Synthesis of cis‐3‐methyl‐4‐aminopiperidine Derivatives

A facile approach for the preparation of cis‐3‐methyl‐4‐aminopiperidine derivatives is described. The synthesis was carried out via regioselective ring opening of N‐benzyl‐3‐methyl‐3,4‐epoxi‐piperidine (8), which can be easily obtained in two steps from the corresponding N‐benzyl‐pyridinium salt (5). Seven new cis‐3‐methyl‐4‐amino and amido piperidines compounds were obtained.     

A New Route for the Synthesis of N-Substituted Diketopiperazine Derivatives

Eight N-substituted diketopiperazines (DKPs) were synthesized by solid-phase protocols. The introduction of iminodiacetic acid (Ida) and followed another α-amino acid residue as the precursor of DKP framework made the present synthesis to be very facile and efficient.     

Radical Cyclization Route to the Stereoselective Synthesis of (+)‐trans‐Cognac Lactone and (+)‐trans‐Aerangis Lactone

Stereoselective total synthesis of two chiral lactones, (+)‐trans‐cognac lactone (1b) and (+)‐trans‐aerangis lactone (2c), has been achieved from the same intermediate using a radical‐based cyclization route.     

Synthesis of C‐Glycosyl Phosphate and Phosphonate,Analogues of N‐Acetyl‐α‐d‐Glucosamine 1‐Phosphate

Synthesis of α‐C‐ethylene phosphate and phosphonate as well as α‐C‐methylene phosphate analogues of N‐acetyl‐α‐d‐glucosamine 1‐phosphate is reported starting from the common perbenzylated 2‐acetamido‐2‐deoxy‐α‐C‐allyl glucoside. Anomerisation of the corresponding amino α‐C‐glucosyl aldehyde to the β‐aldehyde was observed. Thus, both amino α‐ and β‐C‐glucosyl methanol were obtained after reduction.     

A New Route for Synthesis of Entecavir

2-Amino-1,9-dihydro-9-[(1S,3R,4S)-4-hydroxy-3-(hydroxymethyl)-2-methylenecyclopen tyl]-6H-purin-6-one (entecavir, Scheme 1) is a novel carbocyclic 2-deoxyguanosine analog drug which has potent and selective anti hepatitis B virus (HBV) activity1-3. Entecavir is also effective against lamivudine-resistant YMDD mutants4. The US Food and Drug Administration (FDA) approved entecavir as a new preferred drug for the treatment of HBV after lamivudine in March, 2005. Scheme 1 The structure o…     

Synthesis of the C‐Glycoside of Methyl α‐d‐Altropyranosyl‐(1→4)‐α‐d‐glucopyranoside

The C‐glycoside of methyl α‐d‐altropyranosyl‐(1→4)‐α‐d‐glucopyranoside 2 was prepared in a convergent fashion, from readily available precursors, 4‐O‐tert‐butyldiphenylsilyl‐1,2‐O‐isopropylidene‐d‐erythro‐S‐phenyl monothiohemiacetal 13 (five steps from D‐ribose) and the known acid, methyl 2,3,6‐tri‐O‐benzyl‐4‐C‐(carboxymethyl)‐4‐deoxy‐α‐d‐glucopyranoside 17 (seven steps from methyl α‐d‐glucopyranoside). The key reactions in the synthesis are the oxocarbenium ion cyclization of thioacetal‐enol ether 19 to a C1 substituted glycal 20, and the stereoselective hydroboration of 20 to the α‐C‐altroside 21.     

Synthesis and Characterization of Alkyl and Aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines: X‐Ray Structures of Ethyl and Cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine

Abstract

We have synthesized and characterized a series of alkyl and aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines through a high‐yield, three‐step procedure starting from 4‐methylquinolin‐2‐ol. Nitration using concentrated nitric/sulfuric acids, followed by chlorination in phosphorus oxychloride, yielded 2‐chloro‐4‐methyl‐6‐nitro‐quinoline. All of the intermediates and aminated products have been characterized by multinuclear (¹H and ¹³C) NMR spectroscopy, elemental analysis, and, in the case of the two title compounds (ethyl and cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine), a single crystal X‐ray structure was obtained to verify the nature of the new materials.     

Uncatalyzed and Solvent‐Free Process for the Synthesis of 1,4‐Diarylquinoline Derivatives

The uncatalyzed and three‐component reaction of arylaldehyde, malonodinitrile, and 3‐arylamino‐5,5‐dimethylcyclohex‐2‐enone at 160 °C under solvent‐free conditions gave 1,4‐diarylquinoline derivatives in high yields.     

Synthesis and Practical Use of 1H‐1,2,3‐Benzotriazole‐5‐carboxaldehyde for Reductive Amination

A reliable synthetic procedure to obtain multigram quantities of 1H‐1,2,3‐benzotriazole‐5‐carboxaldehyde has been developed. This material can be used in reductive amination reactions with primary and secondary amines to provide good to excellent yields of the desired products without protection of the starting material.     

Synthesis of New N‐(5‐Oxo‐2,5‐dihydro)pyrrol‐3‐yl Glycines and N‐(5‐Oxo‐2,5‐dihydro)pyrrol‐3‐yl Glycines Esters

Following our efforts towards the synthesis of new potential inhibitors of Xanthine Dehydrogenase (XDH), we describe here a general method for the preparation of N-(5-oxo-2,5-dihydro)pyrrol-3-yl glycines and N-(5-oxo-2,5-dihydro)pyrrol-3-yl glycine esters from glycine ethyl ester hydrochloride and various 4-hydroxy-5-oxo-2,5-dihydro-1H-pyrrole-3-carboxylic acid esters and carbonitriles.