Stereospecific synthesis of (+)-oxybiotin from D-xylose. Preparation of the final chiral (+)-oxybiotin precursor

A stereospecific synthesis of 2(S)-carbomethoxy-butyl-3(R), 4(S)-diacetamido-tetrahydrofurane (11), the final chiral precursor in a new synthesis of (+)-oxybiotin has been achieved from 2, 5-anhydro-D-xylose derivative1.     

Further new rearranged lanostanoids from the seeds of Abies mariesii and A. firma

In addition to reported 17,14-friedo lanostane type (I) of triterpene further triterpenes having new rearranged lanostane skeletons, 17,13-friedo lanostane (II) and 8(14→13R) abeo-17,13-friedo lanostane (III), have been isolated from the seed of Abiesmariesii. The skeletons I and II were also found to occur in A. firma. Their structures have been elucidated by spectral and X-ray diffraction analyses.     

Phytoecdysteroids of Rhaponticum carthamoides. II. Rhapisterone B

A new ecdysteroid (rhapisterone B) has been isolated from the seeds ofRhaponticum cathamoides (Willd.) Iljin. (familyCompositae). It has been shown that it is 2β, 3β, 11α, 14α, 20R, 24ξ-hexahydroxy-5β-cholest-7-en-6-one. Institute of the Chemistry of Plant Substances, Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 806–808, November–December, 1991.     

Terpenoids of Crepis tectorum. Molecular and crystal structure of the sesquiterpene lactone 8-epideacylcynaropicrin

Sesquiterpene lactones of the guaianolide type — isolipidiol (I) and 8-epideacylcynaropicrin (II) — have been isolated from narrow-leaf hawk's-beard,Crepis tectorum L. On the basis of the results of an x-ray experiment the structure of (1R, 3S, 5R, 6R, 7R, 8R)-3,8-dihydroxy-cis,trans-guaia-4(15),10(14),-11(13)-trien-6,12-olide is proposed for (II).Institute of Organic Synthesis and Coal Chemistry, Kazakh Academy of Sciences, Karaganda. A. N. Nesmeynaov Institute of Organometallic Compounds, Russian Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 638–642, September–October, 1991.     

HPLC Separation of the Diastereomeric Glutathione Adducts of Styrene Oxide

Abstract

The four diastereomeric thioether adducts resulting from the addition of glutathione to racemic styrene oxide were separated on a Radial Pak C₁₈ column using pH 7 Tris-phosphate buffer solution containing methanol as eluent. The benzylic thioether (1) eluted earlier than the benzylic alcohol (2) regioisomers. A complete stereochemical profile was established with the first eluting stereoisomer assigned as (S,R)-1, followed by (R,R)-1, (S,R)-2, and (R,R)-2,. The diastereomers with S configuration at the benzylic carbon emerged first for each set of regioisomers. The use of glutathione as a chiral probe for the analysis of enantiomerically enriched epoxides was illustrated with β-methylstyrene oxide formed from (1R, 2S)-N,N-dimethylephedrium bromide during the course of a chiral phase-transfer synthesis of oxiranes.     

Structure of new sesquiterpene lactones from Inula germanica

Summary It has been established that the substance isolated previously fromInula germanica L. is a mixture of two new sesquiterpene lactones: germanin A and germanin B.On the basis of chemical reactions and a study of IR, UV, NMR, and mass spectra, structures (I) and (XVI), respectively, are proposed for germanin A and germanin B.All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 578–589, September–October, 1974.     

Enantiospecific syntheses of deoxymannojirimycin,fagomine and 2r,5r-dihydroxymethyl-3r,4r-dihydroxypyrrolidine from D-glucose

Methyl 2-azido-3-O-benzyl-2-deoxy-α-D-mannofuranoside (4), readily available from D-glucose, is a common intermediate in the enantiospecific syntheses of deoxymannojirimycin [1,5-dideoxy-1,5-imino-D-mannitol](l), fagomine [1,2,5-trideoxy-1,5-imino-D- arabino hexitol] (2) and 2R,5R-dihydroxymethyl-3R,4R-dihydroxypyrrolidine (3); these syntheses establish the absolute configurations of (2) and (3).     

Phospha-alkynes - Useful Building Blocks in Organic Chemistry1

Abstract

The syntheses of phospholes (7, [3+2]-cycloaddition), bicyclophosphaalkenes (17, [4+2]-cycloaddition), and phosphabenzenes (15, [4+2]-cycloaddition followed by an extrusion process) starting from the phosphaalkynes (4) are described. The 2–Dewar phosphabenzene 18, obtained from the cyclobutadiene 21 and 4 (R =^tBu), is the starting material for the synthesis of the valency isomers 19, 20, 22, and 23.     

Lead Tetraacetate Fragmentation of Loganin Aglucone O-Metheyl Ether and its Stereoisomers

During the investigation into methods of converting loganin (1) into secologanin (2, R=β-D-glucose), the lead tetraacetate fragmentation reaction¹ of the four diastereomeric loganin aglucone O-methyl ethers 4, 6, 9, and 11, was studied.     

Alkaloids of Rauwolfia species growing in Vietnam

Reserpine, ajmaline, serpentine, ajmalicine, isoreserpiline, and other alkaloids have been isolated from the roots ofRauwolfia cambodiana Pierre ex Pitard,R. verticillata Baill. andR. serpentina Benth.R. vomitoria Afz. was the richest in alkaloids.Leningrad Institute of Pharmaceutical Chemistry. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 813–816, November–December, 1991.     

Syntheses of Trehalose Monomycolate and Related Compounds,and Their Lethal Toxicity and Adjuvant Activity

Five monoesters, 6-O-mycoloyl-α, α-treha lose (TMM), 6-O-mycoloyl-D-glucose (GlcM), 6-O-mycoloyl-N-acetyl-D-glucosamine (GlcNAcM), 5-O-mycoloyl-D-arabinose (AraM) and 6-O-mycoloyl-D-galactose (GalM), were synthesized by use of mycolic acid isolated from Mycobacterium tuberculosis strain Aoyama B. Their toxicity and macrophage activating ability were examined in mice. A single intravenous administration of 400 μg of TMM in 9% oil-in-water emulsion killed 8 of 8 treated mice. The other analogs showed less lethal toxicity to mice at the same dose. Tumoricidal activity of mouse peritoneal macrophages was induced by intraperitoneal injection of TMM, GlcM, and GlcNAcM, respectively.     

Synthesis of α-aryloxy-2,4-dihydroxyacetophenone 4-O-β-D-glucopyranosides and their conversion into 3-aryloxy-7-glucosyloxychromones

The hydrolysis of the glycoside quisqualoside B, isolated from the herbAstragalus quisqualis Bunge, has given the new cycloartane triterpenoid quisquagenin, which has the structure of 20(R),24(S)-epoxycycloartane-3,16,25-triol.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 527–532, July–August, 1987.     

Triterpene glycosides of Thalictrum squarrosum. IV. Structures of squarrosides A1, A2, B1, and B2

Four new cycloartane glycosides have been isolated from a methanolic extract ofThalictrum squarrosum Stephan ex Willd.: squarroside A1 (I) — (21R, 22S, 23R)-3β-(β-D-glucopyranosyloxy)-21α-methoxy-21,23-epoxycycloart-24-ene-22β,30-diol, C₃₀H₆₀O₁₀; squarroside A2 (II) — the (21S)-epimer of compound (I); squarroside B1 (III) (21R, 22S, 23R)-3gb-[O-α-L-rhamnopyranosyl-(1 → 6)-β-D-glucopyranosyloxy]-21α-methoxy-21,23-epoxycycloart-24-ene-22β,30-diol, C₄₃H₇₀O₁₄; and squarroside B2 (IV) — the (21S)-epimer of compound (III). The proposed structures were determined on the basis of¹H and¹³C NMR spectroscopy, FAB mass spectrometry, and chemical transformations. Irkutsk Institute of Organic Chemistry, Siberian Branch, USSR Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 516–523, July–August, 1989.     

Asymmetric Synthesis of Aryl 2-Piperidyl Methanols from a Chiral α-Aminonitrile Precursor

Synthesis of enantiomerically pure phenyl 2-piperidyl methanols from a convenient chiral α-aminonitrile 1 is described. Reaction with aldehydes of the anion generated from 1 leads to threo (αR, 2R) products, whereas treatment of 1 with organolithium reagents affords erythro (αR, 2S) compounds.     

Steroids of the spirostan and furostan series from plants of the genus Allium. XXV. Structure of anzurogenin B from Allium suvorovii and Allium Stipitatum

A new genin of the spirostan series — anzurogenin B having the structure of 2,5-epoxy-(25R)-spirostan-3,6-diol — has been isolated form the collective fruit of the cocultivatedAllium suvorovii Rgl. andAllium stipitatum Rgl. (family Liliaceae).Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 218–221, March–April, 1988.     

Insect pheromones and their analogues XLIII. Chiral pheromones from (S)-(+)-3,7-dimethylocta-1,6-diene 3. Synthesis of (4R)-4-methylnonan-1-OL — Sex pheromone of Tenebrio molitor and its racemic analogue

Starting from the readily available enantiomerically enriched (S)-(+)-3,7-dimethylocta-1,6-diene (ee ≃ 50%), we have synthesized (4R)-4-methylnonan-1-ol — the sex pheromone of the yellow mealworm bettleTenebrio molitor L. A scheme for synthesizing the racemic analogue of the pheromone from 4-methyltetrahydropyran has been developed. Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 711–714, November–December, 1992.     

A novel approach to the synthesis of 1,2-cis-glycopyranosides

Methyl 3,4,6-tri-O-benzyl-α-D-glucopyranoside and methyl 3,4,6-tri-O-benzyl-β-D-mannopyranoside were directly obtained by m-chloroperbenzoic acid treatment of (Z)-(2R,3R,4R)-6-methoxy-1,3,4-tribenzyloxy-5-hexen-2-ol.     

Triterpenoids from the leaves of the siberian species of birchBetula nana andB. exilis

The compositions of the triterpene fractions of the unsaponifiable part of the ethereal extracts of the leaves ofB. nana andB. exilis have been studied. The leaves ofB. exilis have yielded a new triterpene for which the structure of 3,20(S),25-trihyproxydammar-23-ene is proposed, and a four component mixture of epimers at C-3 and C-24 of the compound 3,20(S),24-trihyproxydammar-25-ene. The composition and ratio of the components of the mixture were determined on the basis of chemical and spectral characteristics.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 352–356, May–June, 1985.     

A Stereoselective Synthesis of (−)-Endo-Brevicomin

A stereoselective synthesis of (1S,5R,7R) (-)-endo-brevicomin by employing Sharpless kinetic resolution method has been described.