Synthesis and structure determination of diastereoisomeric (1R,2R,6S)-6-(3-{[(1RS)-1-(1-adamantyl)ethyl]amino}prop-1-en-2-yl)-3-methylcyclohex-3-ene-1,2-diols

Epimeric (1R,2R,6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol derivatives containing a rimantadine residue have been synthesized, and their steric structure has been determined using NOESY technique and DFT quantum chemical calculations.     

Oxidation of (1<Emphasis Type="Italic">S</Emphasis>,5<Emphasis Type="Italic">R</Emphasis>,7<Emphasis Type="Italic">R,S</Emphasis>)-(4,7-dimethyl-6-oxabicyclo[3.2.1]oct-3-en-7-yl) methanol with pyridinium chlorochromate

The oxidation of (1S,5R,7R,S)-(4,7-dimethyl-6-oxabicyclo[3.2.1]oct-3-en-7-yl)methanol epimeric at the C⁷ atom resulted in scalemic (5R)-5-acetyl-2-methylcyclohex-2-en-1-one.     

Skeletal rearrangements of <Emphasis Type="Italic">cis</Emphasis>-(-)-7,8-epoxycarveol derivatives promoted by triethylsilyl trifluoromethanesulfonate

Diastereoisomeric couples of (1R,5R,6RS)-2,6-dimethyl-7-oxabicyclo[3.2.1]oct-2-en-6-ylmethanols and their epoxide precursors, (5R,2′RS)-2-methyl-5-(2-methyloxiran-2-yl)cyclohex-2-en-1-ols, in the presence of triethylsilyl trifluoromethanesulfonate underwent [3.2.1]→[3.3.1] skeletal rearrangement with formation of scalemic mixtures of (1R,5R,6R)- and (1R,5R,6S)-2,6-dimethyl-6-triethylsiloxy-8-oxabicyclo[3.3.1]non-2-enes; the (6R)-stereoisomer was isolated as individual substance.     

Synthesis of (1<Emphasis Type="Italic">R</Emphasis>,2<Emphasis Type="Italic">R</Emphasis>)-1,2-bis-(5-(4-hydroxynaphthalen-1-ylazo)-[1,3,4]thiadiazol-2-yl)-ethane-1,2-diol

In this study, (1R,2R)-1,2-bis-(5-amino-1,3,4-thiadiazol-2-yl)ethane-1,2-diol (2), was synthesized by using (2R,3R)-(+)-Tartaric acid (1) as starting compound. Then the diazo component 3 was obtained from 2 and 1-naphthol. In addition, the structures of the synthesized compounds 2 and 3 were confirmed by elemental analyses, IR, ¹H-NMR, and ¹³C-NMR spectra. __________ Published in Kimiya Prirodnikh Soedinenii, No. 5, pp. 465–466, September–October, 2005.     

Diamidophosphite based on (1<Emphasis Type="Italic">R</Emphasis>,2<Emphasis Type="Italic">R</Emphasis>)-1,2-bis(3-hydroxybenzamido)cyclohexane in Pd-catalyzed enantioselective allylation

Diamidophosphite ligand bearing (1R,2R)-1,2-bis(3-hydroxybenzamido)cyclohexane fragment and stereogenic phosphorus atoms in the 1,3,2-diazaphopholidine cycles was synthesized. Catalytic performance of this ligand was evaluated in asymmetric allylic substitution. In the reactions involving (E)-1,3-diphenyl allyl acetate as a substrate, up to 94% ee in alkylation with dimethyl malonate and up to 68% ee in amination with pyrrolidine was achieved in the presence of this ligand.     

Synthesis of isomeric 2-oxazolidinones from (1<Emphasis Type="Italic">R</Emphasis>,2<Emphasis Type="Italic">R</Emphasis>)-and (1<Emphasis Type="Italic">S</Emphasis>,2<Emphasis Type="Italic">S</Emphasis>)-2-amino-1-(4-nitrophenyl)-1,3-propanediols

A synthesis is reported for (4R,5R)-and (4S,5S)-4-hydroxymethyl-5-(4-nitrophenyl)oxazolidin-2-ones and (1′R,4R)-and (1′S,4S)-4-[hydroxy(4-nitrophenyl)methyl]oxazolidin-2-ones from (1R,2R)-and (1S,2S)-2-amino-1-(4-nitrophenyl)-1,3-propanediols. The effect of the experimental conditions on the formation of these compounds was studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1562–1570, October, 2007.     

Synthesis of chiral glycolurils from (<Emphasis Type="Italic">S</Emphasis>)-(+)- and (<Emphasis Type="Italic">R</Emphasis>)-(-)-1-<Emphasis Type="Italic">sec</Emphasis>-butyl-3-methylurea

Chiral dialkyl- and tetraalkylglycolurils have been obtained using chiral (S)-(+)- and (R)-(-)-1-sec-butyl-3-methylurea as starting materials. The diastereomer (S)-(+)-2,6-di-sec-butyl-4,8-dimethyl-2,4,6,8-tetraazabicyclo[3.3.0]-octane-3,7-dione was separated into stereoisomers, for the higher melting of which the absolute configuration was determined as (S,S,S,S) by X-ray structural analysis.     

Four new chamigrane sesquiterpenoids from the opistobranch mollusk <Emphasis Type="Italic">Aplysia dactylomela</Emphasis>

Four new chamigrane sesquiterpenoids, (6S,10S)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5.5]undec-2-ene-4-one, (4S,6S,10S)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5.5]undec-2-ene-4-ol, (3R,4S,6S,10R)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5.5]undecane-3,4-diol, and (6S,7S,11R)-2-chloro-3,7,11-trimethyl-10-methylidenespiro[5.5]undec-2-ene-7-ol, were isolated from the sea hare Aplysia dactylomela. The chemical structures of new compounds were established by NMR spectroscopy and mass spectrometry. The cytotoxic activity of some of the obtained compounds against promyelocytic HL-60 and monocytic THP-1 leukemia cells was demonstrated.     

Features of catalyzed hydration of 2-(dichloromethyl)-<Emphasis Type="Italic">N</Emphasis>-[(1<Emphasis Type="Italic">R</Emphasis>)-1-phenylethyl)]cyclopent-3-ene-1-carboxamides

The hydration of gem-dichloromethyl group in 2-(dichloromethyl)-N-[(1R)-1-phenylethyl)]cyclopent-3-ene-1-carboxamides in aqueous acetonitrile catalyzed by AgNO₃, FeCl₃·6H₂O, PdCl₂, and BaO was investigated. The optimum results were obtained at the use of BaO. It was demonstrated, that Pd-catalyzed reactions initiated intermolecular ether formation from the primary hydration products, bicyclic amides.     

Synthesis of (<Emphasis Type="Italic">S</Emphasis>)-(-)-1,4-diaryl-6-methyl-4-trifluoromethyl-3,4-dihydropyrimidine-2(1<Emphasis Type="Italic">H</Emphasis>)-thiones

(S)-(+)-4-Amino-4-aryl-5,5,5-trifluoropentan-2-one reacted with aryl isothiocyanates containing electron-withdrawing substituents to give (S)-(−)-1,4-diaryl-6-methyl-4-trifluoromethyl-3,4-dihydropyrimidine-2(1H)-thiones.     

Evasteriosides A and B and other sulfated steroids from the Pacific starfish <Emphasis Type="Italic">Evasterias retifera</Emphasis>

Two new polar steroidal glycosides identified as sodium (20R,22E,24R,25S)-3-O-(β-d-xylopyranosyl)-24-methyl-5α-cholest-22-ene-3β,6β,8,15α,26-pentol 26-sulfate (evasterioside A) and sodium (20R,22E)-24-O-(β-d-xylopyranosyl)-5α-cholest-22-ene-3β,6β,8,15α,24-pentol 3-sulfate (evasterioside B) were isolated from the Pacific starfish Evasterias retifera collected in the Sea of Japan. Five known compounds, viz., coscinasterioside B, aphelasterioside A, marthasterone 3-sulfate and (20R)-cholest-7-en-3β-ol and cholesterol sulfates, were identified. The structures of the new natural compounds were established using their 2D NMR and mass spectra and some chemical transformations.     

Synthesis and crystal structure of (2<Emphasis Type="Italic">S</Emphasis>,4<Emphasis Type="Italic">S</Emphasis>,5<Emphasis Type="Italic">R</Emphasis>)-2-(5-bromo-2-hydroxyphenyl)-3,4-dimethyl-5-phenyl-1,3-oxazolidines

Condensation of ephedrine alkaloids with 5-bromo-2-hydroxybenzaldehyde was studied, and X-ray diffraction analysis of the synthesized (2S,4S,5R)-2-(2-hydroxy-5-bromophenyl)-3,4-dimethyl-5-phenyl-1,3-oxazolidines was performed.     

Cyclopropanation of methyl (2<Emphasis Type="Italic">E</Emphasis>)-3-[(1<Emphasis Type="Italic">R</Emphasis>,6<Emphasis Type="Italic">S</Emphasis>)-7,7-dimethyl-2-oxo-3-oxabicyclo[4.1.0]hept-4-en-4-yl]prop-2-enoate with dichlorocarbene and diazomethane

Cyclopropanation of methyl (2E)-3-[(1R,6S)-7,7-dimethyl-2-oxo-3-oxabicyclo[4.1.0]hept-4-en-4-yl]prop-2-enoate with dichlorocarbene occurred at the endocyclic double bond, while its reaction with diazomethane in the presence of Pd(acac)₂ involved the exocyclic double bond. The resulting lactones reacted with sodium methoxide in methanol via opening of one cyclopropane fragment.     

Synthesis of (<Emphasis Type="Italic">S</Emphasis>)-(+)-6-aryl-3-acetyl-6-trifluoromethyl-5,6-dihydropyridin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones

(S)-(+)-4-Amino-4-aryl-5,5,5-trifluoropentan-2-ones reacted with ethyl acetoacetate and ethyl trifluoroacetoacetate to give (S)-(+)-6-aryl-3-acetyl(or trifluoroacetyl)-6-trifluoromethyl-5,6-dihydropyridin-2(1H)-ones.     

Humulene and its derivatives from <Emphasis Type="Italic">Betula pendula</Emphasis> buds

Humulene and its derivatives (6R)-hydroxy-α-humulene [(6R)-hydroxy-(1E,4E,8E)-4,8,11,11tetramethylcycloundeca-1,4,8-triene], (6R)-acetoxy-α-humulene [(6R)-acetoxy-(1E,4E,8E)-4,8,11,11tetramethylcycloundeca-1,4,8-triene], a coumaric acid ester, 14-hydroxy-α-humulene [14-coumaroxy(1E,4E,8E)-4,8,11,11-tetramethylcycloundeca-1,4,8-triene], (1E,6R,8E)-4,5-epoxy-6-hydroxy-4,8,11,11tetramethylcycloundeca-1,8-diene, and (6R,9S)-4,11,11-trimethyl-8-methylene-1,4-cycloundecadien-6,9-diol were observed in the hydrocarbon extract of Betula pendula (Betulaceae) buds. The GC retention indices were determined for all identified compounds.     

Synthesis of (2<Emphasis Type="Italic">R</Emphasis>,4<Emphasis Type="Italic">R</Emphasis>)-2-alkyl-3-(2-mercaptobenzoyl)thiazolidine-4-carboxylic acids

Basing on natural amino acid L-cysteine, commercially available aliphatic aldehydes, 2-acetylsulfanylbenzoyl chloride and 2,2′-disulfandiyldibenzoyl dichloride a synthesis was developed of (2R,4R)-2-alkyl-3-(2-mercaptobenzoyl)thiazolidine-4-carboxylic acids, potential antihypertensive compounds, inhibitors of angiotensin transforming enzyme.     

Synthesis of (2<Emphasis Type="Italic">S</Emphasis>,3<Emphasis Type="Italic">S</Emphasis>,4<Emphasis Type="Italic">S</Emphasis>)-2,3-<Emphasis Type="Italic">O</Emphasis>-isopropylidene-4-(methoxycarbonylmethyl)cyclopentan-1-one

(2S,3S,4S)-2,3-O-Isopropylidene-4-(methoxycarbonylmethyl)cyclopentan-1-one was synthesized starting from D-ribose through methyl (Z)-3-(5-acetyl-2,2-acetoxyacetyl-2,2-dimethyl-1,3-dioxolan-4-yl)prop-2-enoate which was subjected to cyclization in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, followed by decarboxylation.     

Screening and Immobilization <Emphasis Type="Italic">Burkholderia</Emphasis> sp. GXU56 Lipase for Enantioselective Resolution of (<Emphasis Type="Italic">R</Emphasis>,<Emphasis Type="Italic">S</Emphasis>)-Methyl Mandelate

Microorganisms producing lipase were isolated from soil and sewage samples and screened for enantioselective resolution of (R,S)-methyl mandelate to (R)-mandelic acid. A strain designated as GXU56 was obtained and identified as Burkholderia sp. Preparing immobilized GXU56 lipase by simple adsorption on octyl sepharose CL-4B, the optimum temperature was shifted from 40 °C (free lipase) to 50 °C (immobilized lipase), and the optimum pH was shifted from 8.0 (free lipase) to 7.2 (immobilized lipase). The immobilized enzyme displayed excellent stability in the pH range of 5.0–8.0, at the temperatures below 50 °C and in organic solvents compared with free enzyme. Enantioselectivity ratio for (R)-mandelic acid (E) was dramatically improved from 29.2 to more than 300 by applying immobilized lipase in the resolution of (R,S)-methyl mandelate. After five cycles of use of immobilized lipase, conversion and enantiomeric excess of (R)-mandelic acid were 34.5% and 98.5%, respectively, with enantioselectivity ratio for (R)-mandelic acid (E) of 230. Thus, octyl-sepharose-immobilized GXU56 lipase can be used as a bio-resolution reagent for producing (R)-mandelic acid.     

Synthesis of 4-[(1<Emphasis Type="Italic">R</Emphasis>,4<Emphasis Type="Italic">R</Emphasis>)-3-Oxo-<Emphasis Type="Italic">p</Emphasis>-menthan-2-ylidenemethyl]benzoic Acid and Its Esters

Carbonylation of (E)-2-(4-halobenzylidene)-p-menthan-3-ones, catalyzed by PdCl₂(PPh₃)₂, gave a distereometric mixure of 4-[(1R,4R)- and (1R,4S)-3-oxo-p-menthan-2-ylidenemethyl]benzoic acids, whose reaction with phenols gave 1R,4R diastereomers of the corresponding esters.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 659–664.Original Russian Text Copyright © 2005 by Drushlyak, Kutulya, Pivnenko, Vashchenko.     

Two new ceramides from <Emphasis Type="Italic">Zephyranthes candida</Emphasis>

Two new ceramides were isolated from the bulbs of Zephyranthes candida. Their structures were established as (2S,3S,4R,13E)-1,3,4-trihydroxy-2-[(2′R)-2′-hydroxytetracosanoylamino]-13-octadecene, named zephyranamide A (1) and (2S,3S,4R)-1,3,4-trihydroxy-2-octacosanoylaminohexadecene, named zephyranamide B (2). The structures of the new compounds were elucidated by spectral techniques including ¹H NMR, ¹³C NMR, as well as HSQC, HMBC, DEPT, and COSY.