An efficient high-yield synthesis of D-ribo-phytosphingosine

[Structure: see text] [4R-[4alpha(S),5alpha]]-2,2-Dimethyl-4-(2-oxo-5-vinyl[1,3]dioxolan-4-yl)oxazolidine-3-carboxylic acid tert-butyl ester 5a, obtained in excellent yield and diastereoselectivity by the alpha-hydroxyallylation of the Garner aldehyde (4), is exploited in a novel high-yield synthesis of D-ribo-phytosphingosine (8), using microwave-enhanced cross metathesis as the key step in the chain elongation.     

An efficient synthesis of the natural tetrahydrofuran pachastrissamine starting from D-ribo-phytosphingosine

[reaction: see text] The natural product pachastrissamine, an anhydrophytosphingosine derivative isolated from various sponges and endowed with cytotoxic activity against several human carcinoma cell lines, was synthesized in three steps and with 72% overall yield from d-ribo-phytosphingosine.     

Efficient synthesis of D-erythro-sphingosine and D-erythro-azidosphingosine from D-ribo-phytosphingosine via a cyclic sulfate intermediate

The synthesis of naturally occurring d-erythro-sphingosine and synthetically useful D-erythro-2-azidosphingosine from commercially available d-ribo-phytosphingosine is described. An important feature of this synthesis is the selective transformation of the 3,4-vicinal diol of phytosphingosine into the characteristic E-allylic alcohol of sphingosine via a cyclic sulfate intermediate.     

An efficient synthesis of 2-hydroxyphenylphosphonates

The high yield conversion of phenols into diethyl 2-hydroxyphenylphosphonates via base catalyzed rearrangement of diethyl phenyl phosphates has been achieved.     

An efficient synthesis of 2-hydroxy-gibberellins

Methyl gibberellate(4) has been converted into 2-epi-gibberellin ₂₉ methyl ester(2) in 48% overall yield by a route avoiding protection of the ring D functionality.     

Efficient and selective synthesis of D-arabino-, D-lyxo-, and D-xylo-phytosphingosine from D-ribo-phytosphingosine

A new high-yield approach to the regio- and stereoselective synthesis of d-arabino-, D-lyxo-, and D-xylo-phytosphingosines from inexpensive D-ribo-phytosphingosine is described. The synthetic methodologies mainly rely on the selective configurational inversion of the stereocenter through a neighboring group participation mechanism.     

The efficient synthesis of substituted 2-methylbenzofurans

Chemistry of Heterocyclic Compounds - The efficient synthesis of substituted 2-methylbenzofurans by aromatization of accessible allyl-substituted cyclohex-2-enones in the presence of iodine...     

An efficient friedel-crafts synthesis of 2-acylbenzofurans

2-(Trimethylsilyl)benzofuran, available quantitatively from benzofuran itself, reacts rapidly with primary, secondary, and tertiary aliphatic carboxylic acid chlorides in the presence of titanium (IV) chloride at low temperature to afford the corresponding 2-acylbenzofurans in excellent yields. This approach offers significant synthetic advantage over existing routes to the title compounds.     

A new and efficient synthesis of 2-azatryptophans

This paper describes a new and simple synthesis of 2-azatryptophans in five steps from 2-ethylaniline. This methodology allows to obtain either the amino acid or the amino ester, according to the treatment and the reaction time, and its scaling up for multigram synthesis.     

A simple and efficient synthesis of 2-alkylazulenes

The annulation method based on 2H-cyclohepta[b]furan-2-ones was applied for the synthesis of 2-alkylazulenes; 2-R-azulene (R = Et, i-Pr, n-Pr, i-Bu). Tropolone p-toluenesulfonate was used as a starting compound. By the two step synthesis, 1-carboxylic-3-cyanoazulene derivatives were obtained. Treatment of 1-carboxylic-3-cyanoazulene derivatives with aq H₂SO₄ resulted in decarboxylation and elimination of cyano group to give 2-alkylazulenes in good yields.     

An efficient palladium catalyzed synthesis of 2-arylbenzothiazoles

A novel and convergent palladium catalyzed synthesis of 2-arylbenzothiazoles has been investigated. The key step in the synthesis is a Suzuki biaryl coupling of 2-bromobenzothiazole with aryl boronic acids to provide a variety of 2-arylbenzothiazole derivatives in good yield. The synthetic utility of this methodology is demonstrated by the synthesis of 2-(4-aminophenyl)-6-methoxybenzothiazole, a PET probe precursor for the in vivo imaging of Alzheimer's disease.     

邻位取代1，2－二苯乙烯催化不对称二羟基化反应

邻位取代１，２－二苯乙烯催化不对称二羟基化反应张生勇，孙晓莉（第四军医大学化学教研室西安７１００３２）关键词　不对称二羟基化，手性二醇近年催化的反式稀烃的不对称二羟基化反应取得明显进展［１］，但催化的邻位取代的１，２－二苯乙烯类化合物的不对称二羟基化...     

Reaction of 2-methoxy-3H-azepine with NBS: efficient synthesis of 2-substituted 2H-azepines

[reaction: see text] The reaction of 2-methoxy-3H-azepines, in the presence or absence of a nucleophile, with N-bromosuccinimide (NBS) gave a regioselective 1,4-adduct from which the corresponding 2H-azepine derivatives were formed via base-promoted hydrogen bromide elimination, generally in moderate to quantitative yield. Competitive formation of 4-bromo-2-methoxy-3H-azepine by electrophilic substitutuion or 3H-azepin-2-yl 2H-azepin-2-yl ether by transetherification was minimized at lower reaction temperatures. Quantitative substitution of 2-(2',4',6'-trichlorophenoxy)-2H-azepine derivatives, formed in moderate yield from the respective 3H-azepine and NBS in the presence of 2,4,6-trichlorophenol (TCP), by various nucleophiles gave the corresponding 2-substituted 2H-azepine. Among these nucleophiles were alkanethiol and alkylamine that are not tolerated in the reaction of 3H-azepine and NBS.     

An efficient synthesis of 1-thioamidoalkyl-2-naphthol derivatives

The discovery and development of phosphorus pentoxide supported on silica gel (P₂O₅–SiO₂) as an efficient catalyst has led to an efficient method for the direct preparation of 1-thioamidoalkyl-2-naphthol derivatives in high yields by one-pot, three-component reaction of β-naphthol, aryl aldehydes, and thiourea or N-phenylthiourea at 100 °C under solvent-free conditions. In addition to its simplicity, this method has the ability to prepare a wide variety of the desired products.     

Rapid and efficient synthesis of 2-amino-4H-benzothiazines

The benzothiazine nucleus is a relatively unexplored class of compounds, from the standpoint of both synthetic chemistry and biological activity. We have developed a rapid, high-yielding synthesis of benzothiazines in which a precursor aryl thiourea is prepared on solid phase. Addition of trifluoroacetic acid catalyzes a conjugate addition reaction to form the desired heterocycle and releases it from the resin.     

Novel and efficient synthesis of 4-sulfonyl-2-pyridones

Heterocyclic 4-sulfonyl-2-pyridones represent useful scaffolds for drug discovery, and are also versatile synthetic building blocks. Herein, we describe a novel and efficient synthesis of this heterocyclic ring system utilizing an acid-mediated cyclo-condensation reaction. This synthetic method affords convenient access to structurally diverse N-substituted 4-sulfonyl-2-pyridones in moderate to good yields.     

A simple and efficient synthesis of 2-aryl-substituted benzimidazoles

Sodium hydrogen sulfite was used to promote condensation of o-phenylenediamine with aromatic aldehydes in dimethylformamide to obtain the corresponding 2-arylbenzimidazoles. The procedure is simple and convenient, and it implies inexpensive promoter and is characterized by short reaction time and easy purification of the final products. Published in Russian in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 6, pp. 872–874. The text was submitted by the authors in English.