Synthesis and molecular structure of 3β,28-diacetoxy-(20R)-lupan-29-oic acid

The methyl ester of 3β,28-diacetoxy-(20R)-lupan-29-oic acid was synthesized and its molecular structure was determined.     

Synthesis of 30-Bromo- and 30-Azido-20-oxo-29-nor-3β,28-diacylbetulin Derivatives

Russian Journal of Organic Chemistry - Ozonolysis of 3β,28-diacyloxylup-20,29-enes gave 20-oxo-29-nor-3β,28-diacyloxylup-20,29-enes, which were brominated with molecular bromine in AcOH...     

Synthesis of dimethyl 3-perfluoroalkyl-4-(3-oxo-2-triphenyl-phosphoranylidenbutanylidene)-pent-2-enedioate and its cyclization

The title compounds 5a-5c were prepared via the reaction of methyl 2-perfluoroal-kynoates (4) with methyl 5-oxo-4-(triphenylphosphoranylidene)hex-2-enoate (3), which was obtained from the reaction of methyl propynate (2) with acetylmethylenetriphenylphosphorane (1) at -5-0℃. Intramolecular elimination of Ph3PO took place when compound 5 was heated in aqueous methanol at 115-120℃ in sealed tube, yielding dimethyl 2-trifluoromethyl-4-methylisophthalate (6a) from 5a and methyl 5-acetyl-4-hydroxy-2-heptafluoropropanylbenzoate (6b) from 5b, respectively. The structures of compounds 5, 6a and 6b were confirmed by IR, MS, 1H NMR, 19F NMR and 13C NMR spectroscopy and elemental analyses. Rection mechanisms for the formation of compounds 5, 6a and 6b were proposed.     

Synthesis of aminium 23,24,24-tricyano-3β-hydroxy-20-oxo-21-nor-17β-cholane-5,21-dien-24-ides from tetracyanoethylated pregnenolone

Russian Journal of Organic Chemistry - Reactions of tetracyanoethylated pregnenolone with ammonia and amines in anhydrous medium at reduced temperature afforded new ionic pregnenolone derivatives,...     

Synthesis and reactivity of 3-(trichlorogermyl)propanoic acid and 3-(triphenylgermyl) propanoic acid

3-(Trichlorogermyl)propanoic acid (la) reacts with phenylmagnesium bromide in malar ratio 1:4 to give 3-(triphenylgermyl)propanoic acid (2a).In the compounds la and 2a theβ-carboxylic functional group shows some unusual properties when they react with excess of phenylmagnesium bromide.The compound la reacts with phenylmagnesium bromide in molar ratio 1:5 to give phenyl 2-(triphenylgermyl)ethylketone (3a) and in molar ratio 1:6 to give l,l-diphenyl-3-(triphenylgermyl)propanol (4a).The compound 2a reacts with phenylmagnesium bromide in molar ratio 1:2 to give 3a and in molar ratio 1:3 to give 4a also.Dehydration of the compound 4a with dilute hydrochloric acid seems especially easy.Moreover,the compound la reacted with phenylmagnsium bromide in molar ratio 1:6,then the mixture was treated with dilute hydrochloric acid to give 1,1-diphenyl-3-(triphenylgermyl)-1-propene (5a) in one pot reaction.Alkyl Ge-C bond in the compound 5a can be cleaved selectively by lithium aluminium hydride ( LiAlH4) in good yiel     

β,β-Difluoro analogs of α-oxo-β-phenylpropionic acid and phenylalanine

A simple three-step procedure converted the readily accessible (2-bromo-1,1-difluoroethyl)arenes (2) into α-aryl-α,α-difluoroacetaldehydes (1). Subsequent hydrocyanation, hydrolysis, oxidation and again hydrolysis afforded β-aryl-β,β-difluoro-α-oxopropionic acids (3). Reductive amination transformed the oxoacids 3 into a separable mixture of α-hydroxyacids 11 and racemic β,β-difluoro-β-phenylalanine derivatives (4). Enantiomerically pure β,β-difluorophenylalanine (l-4a) was obtained when α,α-difluoro-α-phenylacet-aldehyde (1a) was condensed with homochiral 1-phenylethylamine, hydrogen cyanide added to the resulting imine, the diastereomeric mixture thus produced hydrolyzed to the carboxamides (15) which were found to be separable by fractional crystallization or chromatography. The pK_a values of the β-aryl-β,β-difluoroalanines (4) were measured and biological profile of the latter probed. 3-(4-Chlorophenyl)-3,3-difluoro-2-oxopropionic acid (4c) proved to be a potent (K_i 27 μM) and selective inhibitor of arogenate dehydratase, a key enzyme catalyzing the last step of the phenylalanine biosynthesis.     

Synthesis of 3-aminopropyl glycosides of branched β-(1→3)-glucooligosaccharides

Russian Chemical Bulletin - The synthesis of branched β-(1→3)-glucooligosaccharides bearing a β-d-glucose residue at position 6 of one of the monosaccharides of the linear chain at...     

Synthesis of ( ) 8-O-Cinnamyl-p-chlorogoniotriol and its Analogues

HowiinolAI',anovellactoneisolatedfromtheethanolicextractsoftherootandsternbarkofGoniolhanlush()TI)iiMerr.(Annoaceae)inourlaboratory.hasbeenshowntopossesssignificantantitullloractivitiestowardhumantumor117vilroandI,71'if'oandfoxytoxlcit}.Recently.wehavesynthesized1anditsderivativeswitllditTerentestergroupsstartingfromcommerciallyavailablea-D-glucoheptonic-y-lactone.Inordertotindtheirrelationshipofstructureandactivityandtosearchfordrugswithmorepotentantitumoractivity.wehavesynthesized( )8-O-…     

A convenient synthesis of 2β,3α-dihydroxyurs-12-en-28-oic acid as a natural diastereoisomer of corosolic acid

2β,3α-Dihydroxyurs-12-en-28-oic acid（6） is a naturally occurring diastereoisomer of corosolic acid with glycogen phosphorylase inhibitory activity.A new strategy for the semi-synthesis of 6 was developed.Using the commercially available ursolic acid（1） as the starting materials,6 was synthesized through five facile reactions with a high stereoselectivity and an overall yield of 47.3%.The structure of 6 was confirmed by optical rotation.ESI-MS,¹H NMR and ¹³C NMR data.     

Synthesis of 3-deoxy-d-manno-2-octulosonic acid (Kdo) and d-glycero-d-talo-2-octulosonic acid (Ko) and their α-glycosides

Reaction of 2,3:5,6-di-O-isopropylidene-d-mannofuranose 1 with C-2 lithio derivatives of glyoxylate mercaptal in the presence of MgBr₂ afforded d-glycero-d-galacto-2-octulosonates 2 and 3, respectively. Their 3-O-deoxygenation led to Kdo. N-Iodosuccinimide treatment of 3 gave thioglycoside 11 directly, which was transformed into Ko derivative 12 via epimerisation of the 3-hydroxy group. 3-O-Benzoylation of 12 and then transformation into phosphite furnished 15, an efficient glycosyl donor. Reaction of 15 with 6-O-unprotected glucosamine derivative 22 as acceptor gave α-glycoside 23, which was successfully transformed either into Kdo-disaccharide 27 or into Ko-disaccharide 29.     

Synthesis and Bioactivity of Isosteviol Derivatives： A Facile Method for Preparation of Ent-16α-hydroxy-15β-hydroxymethylbeyeran-19-oic Acid

In this paper, two new compounds, ent-16α-hydroxy-15β-hydroxymethylbeyeran-19-oic acid 4 and its ethyl ester 5 were synthesized in good yield with a facile method that has never been reported. The mechanism of this reaction was discussed and the mono-hydroxymethylation of carbonyl compound with two α-hydrogens via Tollens＇ reaction was firstly achieved. Compounds 2-5 were tested for activity of inhibition against glycosidases, among which 5 displays good inhibition of β-glucosidase and α-mannase, respectively.     

Synthesis and reactions of 9-hydroxy-(α-alkoxycarbonylalkyl)-4-azafluorenes

The Reformatsky reaction with 4-azafluorenone has given 9-hydroxy-9-(-alkoxycarbonylalkyl)-4-azafluorenes. The course of this reaction with respect to the -haloester used, and the conversion of these hydroxyesters into hydroxy- and ,-unsaturated acids have been examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 81–85, January, 1991.     

Convenient synthesis of mono- and di-β-hydroxy-β-bis(trifluoromethyl)-(di)imines from β-hydroxy-β-bis(trifluoromethyl)-ketones and (di)amines

A series of novel β-hydroxy-β-bis(trifluoromethyl)-imines (2a-j) and di(β-hydroxy-β-bis(trifluoromethyl))-diimines (3a-f) were prepared in moderate to good yields via a simple two-step approach: first, β-hydroxy-β-bis(trifluoromethyl)-ketones (1a-c) were obtained by a catalyst-free aldol reaction between liquid hexafluoroacetone sesquihydrate and ketones (acetone, acetophenone, and pinacolone, respectively); then, condensation of the latter fluorinated β-ketols 1a-c with primary amines or diamines was achieved in the presence of Lewis (montmorillonite, InBr₃, La(OTf)₃) or Brönsted (PTSA) acid catalysts. The molecular structures of mono- and di-β-hydroxy-β-bis(trifluoromethyl)-(di)imines 2e,h and 3a,f were determined and found to exhibit strong intramolecular (R)N?H-O hydrogen bonding.     

Synthesis of biologically active (-)-dehydroiso-β-lapachone and the determination of its absolute configuration

Synthesis of dehydoriso-β-lapachone (1) in both racemic and enantioenriched forms is achieved starting from reduced naphthoquinone equivalents. As for the synthesis of enantioenriched dehydroiso-β-lapachone, introduction of the asymmetric center was carried out by catalytic asymmetric epoxidation of the unfunctionalized trisubstituted olefin using Shi epoxidation diketal catalyst. The construction of isopropenylfurano-1,2-(β)-naphthoquinone was carried out by acidic ring-opening reaction of the epoxynaphthalene and the following diammonium cerium(IV) nitrate (CAN) oxidation. The absolute configuration of naturally occurring (-)-dehydroiso-β-lapachone was finally determined as (R) by comparing the measured optical rotation value of the synthetic (R)-dehydroiso-β-lapachone.     

3,28-Diacetoxylup-20(29)-ene-30-oic Acid and Its ω-Bromoalkyl Esters

Russian Journal of Organic Chemistry - A convenient procedure has been developed for the synthesis of 3β,28-diacetoxylup-20(29)-en-30-oic acid via oxidation of 3β,28-di-O-acetylbetulin...     

Synthesis of 24-Methylene-cholest-5-ene-7-oxo-3β,19-diacetate

24-Methylenecholest-5-ene-7-oxo-3β,19-diacetate 5 was synthesized starting from stigmasterol via twelve step reactions in 4.1% overall yield. It can be served as a key intermediate for the synthesis of 24-methylenecholest-5-ene-3β,7β,19-mol 1, a naturally occuring polyhydroxylated sterol with potential biological activity.     

Synthesis and antitumor activity of a group of diosgenyl glycosides

Using orthogonal protection-deprotection glycosylation strategy, a series of diosgenyl glycosides with same of monosaccharides component but different in sequence were synthesized. The antitumor activity in vitro of synthesized diosgenyl glycosides was evaluated by standard MTT assay. It was observed that diosgenyl glycosides with a rhamnopyranosyl at C2′ of glucopyranosyl residue show potent antitumor activity in vitro.