Synthesis of heterocycles from the methyl ester of dehydroacetic acid

Conclusions The corresponding pyranopyrazole and pyranoisoxazole were obtained by the reaction of the methyl ester of dehydroacetic acid with phenylhydrazine and with hydroxylamine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1098–1100, May, 1971.     

Synthesis of methyl ester of 4-bromo-2, 3-butadienoic acid

Conclusions The synthesis of the methyl ester of 4-bromo-2, 3-butadienoic acid was described.Translated from Izvestiya Akadeemii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1494–1495, August, 1965 Original article submitted December 2, 1964     

Hepatoprotective and neuroprotective tocopherol analogues isolated from the peels of Citrus unshiu Marcovich

Three tocopherol analogues methoxytocopherol (1), α-tocopherol (2) and γ-tocopherol (3) were isolated from the peels of Citrus unshiu Marcovich. The protective effects of the isolated compounds against tert-butyl hydroperoxide-induced hepatotoxicity in human liver-derived HepG2 cells and glutamate-induced oxidative stress in HT22-immortalised hippocampal cells were evaluated. Compounds 1–3 were significantly protective in HepG2 cells with EC₅₀ values of 21.22 ± 2.01, 25.21 ± 2.11 and 25.25 ± 1.21 μM, respectively, and in HT22 cells, compounds 1–3 had EC₅₀ values of 20.62 ± 1.36, 6.44 ± 1.65 and 9.52 ± 1.54 μM, respectively.     

Synthesis of a new class of bisheterocycles from phenacylsulfonylacetic acid methyl ester

Novel bisheterocycles, 1,2,3‐selenadiazoles, thiadiazoles and 2H‐diazaphospholes in combination with oxadiazoles, thiadiazoles and triazoles were prepared from phenacylsulfonylacetic acid methyl ester.     

Synthesis of phenyl analog of retinoic acid methyl ester proceeding from 3-(bromomethyl)but-3-enal diethylacetal

Aromatic analog of retinoic acid methyl ester was prepared using a convenient prenylating agent, 3-(bromomethyl)but-3-enal diethylacetal, and Barbier reaction in the key stage of building up the carbon chain of target molecules. A version is offered of the synthesis of methylidene analog of aromatic retinoic acid.     

Synthesis of 1,4-dihydro-2-methyl-4-oxo-3-quinolineglyoxylic acid and related compounds

The synthesis of 1,4-dihydro-1-methoxy or ethyl -2-methyl-4-oxo-3-quinolineglyoxylic acid derivatives are described. α-Acetoxy-1,4-dihydro-1-hydroxy-2-methyl-4-oxo-3-quinolineacetic acid esters ( 7a, 7a ), which are key intermediates, were prepared by catalytic hydrogenation of 2-acetoxy-3-acetyl-4-hydroxy-4-(2-nitrophenyl) crotonic acid lactone ( 6 ) in methanol or ethanol.     

Synthesis of a novel ether-bridged GM3-lactone analogue as a target for an antibody-based cancer therapy

We describe herein the synthesis of a new analogue of the GM3-lactone containing a cyclic ether moiety. The ether moiety was chosen as a replacement for the regular lactone group since it shows high resemblance with the lactone and is completely stable under biological conditions. The cyclic ether moiety was formed by reduction of the corresponding lactone to give the lactol followed by formation of the S,O-hemiacetal and hydrogenation. In addition, we have prepared haptens with a hexanoic acid moiety, which can be used for the preparation of poly- and monoclonal antibodies after binding to BSA or KLH. This is the first example of an analogue of the GM3-lactone which is stable under hydrolytic conditions in vitro and probably also in vivo. Reaction of lactone 18 with a Red/Al derivative led to the lactol 19 which was transformed into the S,O-hemiacetal 20 using 2,2'-bis(pyridinium) disulfide in quantitative yield. Hydrogenation with Raney Nickel gave 21 from which after removal of the protecting group at C-1a the trichloroacetimidate 25 was prepared. Reaction with azidosphingosine to give 26 followed by reduction of the azido group with NHEt3+[(PhS)3Sn], acylation with stearic acid using EDC and removal of the protecting groups led to the desired ether analogue of GM3 lactone 4. In addition the trichloroacetimidate 25 was glycosidated with 6-hydroxyhexanoic acid methyl ester, which was deprotected to give 29. The compound will be used for the preparation of poly- and monoclonal antibodies after coupling with BSA and KLH.     

First total synthesis and absolute stereochemical assignment of vittarilide-A,an antioxidant extractive component isolated from Vittaria anguste-elongata Hayata

The first stereocontrolled synthesis of vittarilide-A and its C5-epimer was completed from d-glucuronolactone. Comparison with the spectroscopic properties reported for authentic material has given a clear indication as to the absolute stereochemistry of the natural vittarilide-A.     

A Selective Synthesis of 3,3-Di-C-(hydroxymethyl)-3-deoxy-furanorono-1,4-lactone in the Formose Reaction

Abstract

The formose reaction, by which a complex mixture of sugars and sugar alcohols (the so-called formose) are produced by the base-catalyzed condensation of formaldehyde, has received much attention in connection with the prebiotic synthesis of carbohydrates² and the microbial utilization of formose.^3–5 Formose, however, has not been useful yet, because of the complexity of this product mixture (Fig. 1a). Therefore, it seemed desirable to make the reaction more selective.     

Synthesis of the dibenzyl ester of tert-butoxycarbonyl-L-alanyl-D-glutamic acid from racemic glutamic acid

M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 865–866, November–December, 1991.     

Synthesis and antiviral activities of novel 1,4-pentadien-3-one derivatives bearing an emodin moiety

A series of 1,5-diaryl-1,4-pentadien-3-one derivatives bearing an emodin group were designed and synthesized by the combination of natural products. The antiviral activities against tobacco mosaic virus (TMV) and cucumber mosaic virus (CMV) in vivo were evaluated. Some of the derivatives displayed promising curative effect and protective activity against TMV. Compound D5 showed appreciable curative bioactivity on TMV approximately of 50% at 306.2 mg/mL, which was superior to ningnanmycin (409.3 mg/mL).     

Synthesis of 1-methyl-3-oxo-7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylic acid methyl ester

A simple and efficient method for the preparation of 1-methyl-3-oxo-7- oxabicyclo[2.2.1]hept-5-en-2-carboxylic acid methyl ester (1) is described. The first step is a highly regioselective Diels-Alder reaction between 2-methylfuran and methyl-3-bromo- propiolate. A remarkably difficult ketal hydrolysis reaction was effected by treatment with HCl, a simple reagent that was shown to be more efficient, in this case, than commonly used more elaborate methods.     

Synthesis of a tetrasaccharide related to the triterpenoid saponin isolated from Schima noronhae

A concise synthesis of a tetrasaccharide related to the cell-growth inhibitory triterpenoid saponin isolated from Schima noronhae is reported. A late stage 2,2,6,6-tetramethylpiperidinyloxy (TEMPO)-mediated oxidation of a primary hydroxyl group to carboxylic acid has been achieved under phase-transfer conditions. Stereoselective glycosylations were carried out using thioglycoside or glycosyl trichloroacetimidate activation using sulfuric acid immobilized on silica (H₂SO₄–silica) in conjunction with N-iodosuccinimide and alone, respectively.     

On the 1,1-elimination of nitrous acid and the loss of hydroxyl from the molecular ion of the methyl ester of γ-nitrobutyric acid

It is shown by D labelling experiments that nitrous acid and hydroxyl, eliminated from the methyl ester of γ-nitrobutyric acid upon electron-impact, contain a γ-hydrogen atom to the extent of ～ 85% and ～ 100%, respectively. The loss of nitrous acid is the third case of a highly specific 1,1-elimination from a molecular ion^1a,1b reported hitherto and arguments are presented for the essential role played by carbomethoxy group in this reaction, i.e. it converts the nitro structure of the molecular ion to its acinitro structure. The results obtained further point to a stepwise character of the McLafferty rearrangement, at least for the present case.     

Synthesis and properties of (6-methyl-2-oxo-4-thioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)acetic acid methyl ester

On interacting of the methyl ester of (6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)acetic acid with the Lawesson’s reagent the corresponding 4-thioxo derivative is synthesized. Its alkylation with methyl bromoacetate has been studied as has its interaction with N-nucleophiles, amines, and hydrazines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 590–594, April, 2007.     

Synthesis of 2,3,5,6-tetrahydro-4H-1,4-thiazin-3-one 1,1-dioxides from methyl (styrylsulfonyl)acetate

Methyl (styrylsulfonyl)acetate ( 1 ) was shown to be a useful building block for the synthesis of 5-phenyl-2,3,5,6–4H-tetrahydro-1,4-thiazin-3-one (2), its 4-amino 3 , and 4-hydroxy 4 derivatives. Their 2-spirocyclopropanes 9, 10 , and 11 , and 2,7-diphenyl-6,7-dihydro-8H-pyrimido[5,4-b][1,4]thiazinc 5,5-dioxide ( 18 ) were also prepared from 1 .