Stereoselective total synthesis of cytotoxic sporiolide A

A simple and highly efficient stereoselective total synthesis of cytotoxic agent sporiolide A has been achieved starting from d-mannitol; the strategy of synthesis utilizes stereoselective zinc-mediated allylation, aldol coupling and ring-closing metathesis as key steps.     

The first total synthesis of sporiolide A

The first total synthesis of the natural cytotoxic agent sporiolide A has been accomplished from D-glucal in 16 steps with 6.1% overall yield. Carbohydrates were applied as the chiral templates to manipulate the absolute configuration during the synthesis. Pyridinium chlorochromate (PCC)-promoted transformation of the cyclic enol-ether to lactone, followed by Yamaguchi esterification and intramolecular ring closure metathesis, greatly facilitates synthesis of the target compound.     

The first total synthesis of sporiolide B

The first total synthesis of natural cytotoxic agent, sporiolide B, is described. d-Xylose was used as the chiral template to pre-control the absolute configuration during the synthesis. Yamaguchi esterification and ring closing metathesis greatly facilitate the target compound accomplishment.     

Asymmetric synthesis of machilin C and its analogue

Full details of the asymmetric total synthesis of erythro-8-O-4′-neolignan, machilin C, and its analogue perseal A are reported. The synthesis was involved in the Sharpless dihydroxylation reaction that occurred with excellent asymmetric induction, and the Mitsunobu reaction which occurred with inversion of the absolute configuration from the threo to the erythro isomer. The synthesis was achieved from simple vanillin in eight to twelve steps.     

Enzymatic synthesis of flavin adenine dinucleotide

A new and simple enzymatic method for the synthesis of flavin adenine dinucleotide (FAD) from flavin mononucleotide by the transadenylylation reaction using microbial cells is described. Among various microorganisms tested,Artherobacter globiformis IFO 12138 and two soil bacteria were selected as useful enzyme sources. Under suitable reaction conditions, the amount of FAD synthesized was 2.25 μmol/mL with cells ofA. globiformis. The transadenylylation reaction could be coupled with the ATP supplying system through a glycolysis process with yeast.     

A convenient synthesis of 3-aryl-3,4-dihydroisoquinolinium salts

A convenient synthesis of the title compounds proceeding via direct Bischler-Napieralski cyclization reaction of the appropriate N,N-dialkylformamides obtained from the adequate imines is described. The reported procedure implies synthetically useful yields and mild reaction conditions.     

New synthesis of isoxazolidines

A new synthesis of 5-substituted isoxazolidines was developed by direct isoxazolidine ring formation of allylic hydroxylamines under acidic conditions. The cyclization process is an electrophilic S_N1 type reaction. The formed carbocation intermediate is stabilized by electron rich groups (i.e., phenyl). A moiety that mediates oxonium ion formation (i.e., para-methoxy) accelerates the rate of product formation.     

Novel synthesis of 2-arylbenzothiazoles

A new method for the synthesis of 2-arylbenzothiazoles by the reaction of dibenzyl disulfides witho-aminothiophenol is suggested. A possible mechanism of the new transformation is discussed. 2-Phenylbenzothiazole can also be prepared by reactions ofo-aminothiophenol with benzyl mercaptane or sodium benzyl thiosulfate. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1887–1890, November, 2000.     

Enantioselective synthesis of (−)-lasubine II

A highly enantioselective synthesis of lythraceae alkaloid lasubine II has been achieved using organo-catalyzed Mannich reaction, Maruoka allylation, and aza-Michael addition as the key steps.     

A facile and convenient approach to the synthesis of 3,5-diaryl-1H-pyrazoles

A simple and convenient one-pot synthesis route is described for the synthesis of 3,5-diaryl-1H-pyrazoles in short reaction times from the reaction of α-epoxyketones with semicarbazide hydrochloride under mild conditions.     

Triton-B catalyzed, efficient one-pot synthesis of dithiocarbazates

A quick and efficient, one-pot synthesis of dithiocarbazates was accomplished in high yields by the reaction of various primary, secondary, and tert. alkyl halides with a variety of substituted hydrazines using the benzyl-trimethylammonium hydroxide (Triton-B)/CS₂ system. The reaction conditions are mild with simpler work-up procedures than the reported methods.     

Stereoselective synthesis of 4-hydroxymethyl-1,3-oxazolidin-2-one derivatives from novel 2-hydroxymethylaziridines

A stereoselective and simple method for the synthesis of trans-2-hydroxymethyl-N-alkyl-1,3-oxazolidin-2-ones is described. The synthesis involved the reduction of trans-aziridine-2-carboxylates with LiAlH₄, followed by a ring opening and a cyclization reaction in the presence of methyl chloroformate to afford the target trans-oxazolidinones in completely regio- and stereoselective process. A plausible reaction mechanism has been proposed involving an S_N1 pathway and a detailed computational study of this mechanistic process has been carried out using theoretical calculations.     

Solvent‐free synthesis of pyrrole derivatives

A one‐pot synthesis of pyrrole derivatives via reaction between activated carbonyl compounds, primary amines, and 1,3‐dicarbonyls under solvent‐free conditions is described. J. Heterocyclic Chem., (2012).     

A simple synthesis of non-solvated galliumtrialkyls

A simple synthesis of non-solvated galliumtrialkyls is proposed based on the reaction of alkyl iodides with a mixture or an alloy of magnesium and gallium in the absence of a solvent or in aliphatic hydrocarbons. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 392–393, February, 1997.     

Direct synthesis of aromatic polyamides

The synthesis of aromatic polyamides, namely poly(p-phenylenetere-phthalamide) and poly(p-benzamide), via phosphorylation reaction has been thoroughly investigated. The effect of reaction temperature, concentration of monomers and reactants, type and concentration of salts, amount of the activator and its stepwise addition have been considered and the optimum reaction conditions found. The resultant synthesis of the above polymers, also in connection with the high purification techniques of all components of the reaction mixture, allowed to reach the highest molecular weights obtained so far by this synthetic way.     

New synthesis of quinolines from lithiated allenes and isothiocyanates

A new route was proposed for the synthesis of quinolines based on the reaction of lithiated allenes with phenyl isothiocyanate.Translated frimIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 3024–3025, December     

Modifications at the 6-O-position of 1-deoxynojirimycin: facile and efficient synthesis of 6-O-alkylated-N-octyl-1-deoxynojirimycin derivatives

A straightforward synthesis of N-alkylated 1-deoxynojirimycin derivatives modified at the 6-O-position has been described. The key intermediate in the synthesis of target compounds was 2,3,4-tri-O-benzyl-1,5-dideoxy-1,5-imino-D-glucitol, which was prepared from 2,3,4,6-tetra-O-benzyl-1,5-dideoxy-1,5-imino-D-glucitol. Optimal conditions have been established for the synthesis of the key intermediate by varying reaction parameters. Reductive amination and subsequent alkylation of the 6-O-position followed by hydrogenolysis were the main reaction steps, which gave target compounds 6-O-ethyl-N-octyl-1,5-dideoxy-1,5-imino-D-glucitol and 6-O-butyl-N-octyl-1,5-dideoxy-1,5-imino-D-glucitol. This synthetic route is flexible and can be useful for the synthesis of other lipophilic iminosugar derivatives.     

Efficient one-pot synthesis of ethyl 2-substitued-4-methylthiazole-5-carboxylates

A new and practical one-pot procedure for the synthesis of several 2-sustituted-4-methylthiazole-5-carboxylates from commercially available starting materials is described. Under mild reaction conditions, some of the products with alkyl group on the 2-amino group or with various groups on 2-substituted phenyl ring were obtained in good yields from ethyl acetoacetate, N-bromosuccinimide, thiourea, or its N-substituted derivatives in an efficient way instead of the traditional two-step reaction.     

Total synthesis of indole and dihydroindole alkaloids. VII. The total synthesis of isovelbanamine, velbanamine, cleavamine, 18beta-carbomethoxycleavamine and catharanthine.

A synthesis of a variety of nine-membered ring intermediates in the cleavaminevelbanamine series is described. The formation of the penultimate intermediate involves a fragmentation reaction in which the cleavamine system is generated from an appropriate rigid pentacyclic Iboga alkaloid derivative. Thus dihydrocatharanthinol tosylate (VIII) on reaction with triethylamine in refluxing benzene undergoes fragmentation to the 5, 18-seco-diene X. This latter substance is then elaborated in various ways to the desired compounds.     

A new synthesis of phthalimidines

A new synthesis of phthalimidines is described. 3-Acyloxy-2-aryl- and 2-acylamino-3-acyloxyphthalimidines were prepared by the reaction of 3-arylaminophthalides or o-formylbenzoic acid acylhydrazones with acetic or propionic anhydrides. Their reactions with O-, N-, S-, and C-nucleophiles were studied. The structure of 2-acetyl(cyanoacetyl)amino-3-acetoxyindolin-1-one was confirmed by X-ray diffraction analysis.