Stereoselective reductive tetraallylation of pyridinecarboxylic acids with triallylborane

Reductive tetraallylation of pyridine-3-and pyridine-4-carboxylic acids with triallylborane in the presence of propan-2-ol proceeded stereoselectively to yieldtrans-2,6-diallyl-3- andtrans-2,6-diallyl-4-(1-allyl-1-hydroxybut-3-en-1-yl)-1,2,5,6-tetrahydropyridines, respectively. Under the same conditions, the reaction with pyridine-2-carboxylic acid gave a mixture oftrans- andcis-2,6-diallyl-2-(1-allyl-1-hydroxybut-3-en-1-yl)-1,2,5,6-tetrahydropyridines in a ratio of 57:43. When 2,6-diphenylpyridine-4-carboxylic acid reacted with triallylborane, only the carboxylic group underwent reductive diallylation. When heated with triallylborane ino-xylene (130–133°C, 7 h),trans-2,6-diallyl-4-(1-allyl-1-hydroxybut-3-en-1-yl)-1,2,3,6-tetrahydropyridine was converted to the correspondingcis-isomer. The stereochemistry oftrans-2,6-diallyl-3-(1-allyl-1-hydroxybut-3-en-1-yl)-1,2,5,6,-tetrahydropyridine was confirmed by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2320–2326, November, 1998.     

A Chemical Study of Burley Tobacco Flavour (Nicotiana tabacum L.) VII. Identification and synthesis of twelve irregular terpenoids,related to solanone,including 7,8-dioxabicyclo[3.2.1]octane and 4,9-dioxabicyclo[3.3.1]nonane derivatives

Twelve novel constituents isolated from Burley tobacco condensate by semi-preparative GLC. have been identified as (E)-3,4-epoxy-5-isopropyl-nonane-2,8-dione ( A ), exo-(1-methyl-4-isopropyl-7,8-dioxabicyclo[3.2.1]oct-6-yl)methyl ketone ( B ), exo-1-(1-methyl-4-isopropyl-7,8-dioxabicyclo[3.2.1]oct-6-yl)-ethanol ( C ), (E)-5-isopropyl-8-hydroxy-8-methyl-non-6-en-2-one ( D ), (E)-5-isopropyl-6,7-epoxy-8-hydroxy-8-methyl-nonan-2-one ( E ), endo-2-(1-methyl-4-isopropyl-7,8-dioxabicyclo[3.2.1]oct-6-yl)-propan-2-ol ( F ), 3,3,5-trimethyl-8-isopropyl-4,9-dioxabicyclo[3.3.1]nonan-2-ol ( G ), (E)-5-isopropyl-non-3-ene-2,8-diol ( H ), 5-isopropyl-nonane-2,8-diol ( I ), (E)-5-isopropyl-8-hydroxy-non-6-en-2-one ( J ), 5-isopropyl-8-hydroxy-nonan-2-one ( K ), and (E)-3-isopropyl-6-methyl-hepta-4,6-dien-1-ol ( L ). Compounds A–K were synthesized from norsolanadione ( 2 ), and compound L from 2-isopropyl-5-oxo-hexanal ( 15 ). The relative configuration of the bicyclic internal acetals B, C, F, G and their δ-keto-epoxide precursors A and E is discussed. All these Burley tobacco flavour components belong to a growing family of metabolites structurally related to solanone ( 1 ). They are believed to arise from the breakdown of cembrene-type precursors.     

Application of Phenyl 1-Selenoglycosides in the Synthesis of a Cell-Wall Tetrameric Fragment of Proteus Vulgaris Strain 5/43

Abstract

DAST-assisted rearrangement of 3-O-allyl-4-O-benzyl-α-l-rhamnopyranosyl azide followed by treatment of the generated fluorides with ethanethiol and BF₃·OEt₂ gave glycosyl donor ethyl 3-O-allyl-2-azido-4-O-benzyl-2,6-dideoxy-1-thio-α/β-l-glucopyranoside. Stereoselective glycosylation of methyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-β-D-glucopyranoside with ethyl 3-O-allyl-2-azido-4-O-benzyl-2,6-dideoxy-1-thio-α/β-l-glucopyranoside, under the agency of NIS/TfOH afforded methyl 3-O-(3-O-allyl-2-azido-4-O-benzyl-2,6-dideoxy-α-l-glucopyranosyl)-4,6-O-benzyli-dene-2-deoxy-2-phthalimido-β-D-glucopyranoside. Removal of the allyl function of the latter dimer, followed by condensation with properly protected 2-azido-2-deoxy-glucosyl donors, in the presence of suitable promoters, yielded selectively methyl 3-O-(3-O-[6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-D-glucopyranosyl]-2-azido-4-O-benzyl-2,6-dideoxy-α-l-glucopyranosyl)-4,6-O-benzylidene-2-deoxy-2-phthalimido-β-D-glucopyranoside. Deacetylation and subsequent glycosylation of the free HO-6 with phenyl 2,3,4,6-tetra-O-benzoyl-1-seleno-β-D-glucopyranoside in the presence of NIS/TfOH furnished a fully protected tetrasaccharide. Deprotection then gave methyl 3-O-(3-O-[6-O-{β-D-glucopyranosyl}-2-acetamido-2-deoxy-β-D-glucopyranosyl)-2-acetamido-2,6-dideoxy-α-L-glucopyranosyl)-2-acetamido-2-deoxy-β-D-glucopyranoside.     

Synthesis of some tolperisone metabolites in racemic and optically active form

1-(4′-Carboxyphenyl)-2-methyl-3-(piperidine-1-yl)-propan-1-one M3, erythro-1-(4′-carboxyphenyl)-2-methyl-3-(piperidine-1-yl)-propan-1-ol M4 and threo-1-(4′-carboxyphenyl)-2-methyl-3-(piperidine-1-yl)-propan-1-ol M5, metabolites of the muscle relaxant tolperisone were synthesized in racemic and optically active forms.     

4-Oxo-3,4-dihydroquinazolinyl- and Benzimidazolylacetonitriles in Annelation Reactions of a Haloquinoline Ring

The interaction of 4-oxo-3,4-dihydroquinazolinyl- and benzimidazolylacetonitriles with 2,6-dihalobenzaldehydes leads to 3-(2,6-dihalophenyl)-2-(4-oxo-3,4-dihydro-2-quinazolinyl)acrylonitriles and 2-(1H-benzo[d]imidazol-2-yl)-3-(2,6-dihalophenyl)acrylonitriles respectively. As a result of intramolecular cyclization of these nitriles 4-halo-12-oxo-12H-quino[2,1-b]quinazoline-6-carbonitriles and 4-halobenzo[4,5]imidazo[1,2-a]quinoline-6-carbonitriles respectively are formed.     

The Terpenoids of Maytenus boaria MOL. (Celastraceae)

The known triterpenoids β-amyrin (= olean-12-en-3β-ol; 22 ), lupeol (= lup-20(29)-en-3β-ol; 17 ), betulin (= lup-20(29)-ene-3β,28-diol; 18 ), lup-20(29)-ene-3β,30-diol ( 20 ), oleanolic acid (= 3β-hydroxyolean-12-en-28-oic acid; 21 ), and betulonic acid (= 3-oxolup-20(29)-en-28-oic acid; 19 ), together with epicatechol (= cis-2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-1-benzopyran-3,5,7-triol; 23 ), 5′-O-methylgallocatechol (= trans-2-(3,4-dihydroxy-5-methoxyphenyl)-3,4-dihydro-2H-1-benzopyran-3,5,7-triol; 24 ), and 4-hydroxybenzaldehyde were isolated from the aerial parts of Maytenus boaria (MOL. ). Additonally, the eight 4,C⁴-dihydro-β-agarofuran sesquiterpenoids 1–8 , one of them a diol with a (4R)-configuration, and compound 9 were present in the extract. The structures of these compounds were established by spectroscopic and chemical means.     

Facile addition of methyl lithium to a 4-vinylpyridine system

The rapid addition of methyl lithium to the 4-vinylpyridine system present in 4-{2,6-dihydroxy-4-(3-methyl-2-octyl)phenyl}-2-methyl-4-(4-pyridyl)but-3-en-2-ol ( 2 ) is reported. The α and β-4-{2,6-dihydroxy-4-(3-methyl-2-octyl)phenyl}-2,3-dimethyl-4-(4-pyridyl)butan-2-ols 4 and 5 formed, are cyclised by heating with 5N hydrochloric acid to trans and cis-3,4-dihydro-5-hydroxy-7-(3-methyl-2-octyl)-4-(4-pyridyl)-2,2,3-trimethyl-2H-1-benzopyran 6 and 7 respectively.     

Synthesis and structure of novel 6-(pyrazol-1-yl)-4-methyl-1H-pyrazolo[3,4-b]pyridin-3-ol derivatives

New 6-(pyrazol-1-yl)pyrazolo[3,4-b]pyridin-3-ol compounds were synthesized by cyclization reaction from 2,6-dichloro-4-methylnicotinonitrile. Their derivatives exist as the 3-hydroxy tautomer. The structure of the compound 1a of one of the resulting compounds was studied in detail by X-ray diffraction.     

Die Cyclopropylcarbinyl-Cyclobutyl-Homoallyl-Umlagerung. I. Teil. Synthese von Tricyclo[3.2.1.02,7]octan-3-ol,endo- und exo-Tricyclo[3.2.1.03,6]octan-4-ol und exo-Bicyclo[3.2.1]-oct-2-en-7-ol

Tricyclo[3.2.1.0^2,7]octan-3-ol ( 1 ) and its 4-isomer 7 were obtained by hydroboration of tricyclo[3.2.1.0^2,7]oct-3-ene ( 5 ). The former alcohol 1 is quantitatively converted to the isomeric alcohol exo-bicyclo[3.2.1]oct-2-en-7-ol ( 3 ) by treatment with aqueous acid. Photolysis of 1-diazo-3-(cyclopent-3-enyl)-propan-2-one ( 12c ) gave a high yield of tricyclo[3.2.1.0^3,6]octan-4-one ( 10a ). Reduction of the latter ketone produced a mixture of endo- and exo-tricyclo[3.2.1.0^3,6]octan-4-ol 2 and 9 , respectively. Oxidation of these secondary alcohols with silver carbonate in benzene furnished a mixture of the ketone 10a and the lactone 14 of 6-hydroxy-bicyclo[2.1.1]heptane-2-carboxylic acid. The latter is thought to be formed by oxydation of the hydrate of the strained ketone 10a .     

Säurekatalysierte Umlagerung von 4-Allyl-cyclohex-2-en-1-olen; Beispiele für ladungskontrollierte [3s, 4s]-Umlagerungen von cyclischen Allylkationen

The acid-catalysed rearrangement of the cyclohex-2-en-1-ols 15 , d₃- 15 , 16 , 17 and 19 , the cyclohexa-2,5-dien-1-ols 20 and 21 , and also the allyl alcohols 22 and 23 (Scheme 3), using 98-percent sulfuric acid/acetic anhydride 1:99 at room temperature, was investigated. From the rearrangement of 4-allyl-4-phenyl-cyclohex-2-en-1-ol ( 15 ), with reaction times greater than 2 hours a single product is obtained, 4-allyl-biphenyl ( 50 ) in 33% yield (Scheme 9). With reaction times below 2 hours the acetate 53 from 15 was isolated, and this could be converted into 50 . The reaction of 2′,3′,3′-d₃-15 in Ac₂O/H₂SO₄ lead to 1′,1′,2′-d₃-50 (Scheme 11). The rearrangement of 4-allyl-4-methyl-cyclohex-2-en-1-ol (16) (Scheme 14) yielded 39% of the corresponding acetate 60 and 30% of 4-allyl-toluene ( 6 ), which also resulted by a rearrangement of 60 under the reaction conditions. These rearrangements are all [3s,4s]-sigmatropic reactions, which proceed via the cyclohexenyl cation a (Scheme 12, R = C₆H₅, CH₃). In Ac₂O/H₂SO₄ the allyl-cyclohexadienes primarely formed subsequently undergo dehydrogenation to yield the benzene derivatives 6 , 50 and d₃- 50 . From the rearrangement of 4,4-diphenyl-cyclohex-2-en-1-ol ( 19 ) at 0° a reaction mixture is obtained which consists of the acetate 55 , 2,3-diphenyl-cyclohexa-1,4-diene ( 57 ) and o-terphenyl ( 56 ) (Scheme 10). Both 55 and 57 are converted under the reaction conditions to o-terphenyl ( 56 ). No 4-(1′-methylallyl)-biphenyl is obtained from the rearrangement of 4-crotyl-4-phenyl-cyclohex-2-en-1-ol ( 17 ). In this case, apart from the corresponding acetate 64 , a single product 5-(1′-acetoxyethyl)-1-phenyl-bicyclo[2.2.2]oct-2-ene ( 65 ) (Scheme 16) was obtained; under the reaction conditions the acetate 64 rearranges to 65 . The rearrangement of 4-allyl-4-phenyl-cyclohexa-2,5-dien-1-ol ( 20 ) gives, as expected, not only 4-allyl-biphenyl ( 50 ) but also 2- and 3-allyl-biphenyl ( 51 and 52 ) and biphenyl (Scheme 13). 4-Benzyl-4-methyl-cyclohexa-2,5-dien-1-ol (syn- and anti- 21 ) gave in Ac₂O/H₂SO₄ at 10° as rearrangement products 93% of 2-benzyltoluene ( 97 ) and 7% of 4-benzyl-toluene ( 98 ) (Scheme 21). Hence [1,4]-rearrangements in cyclohexadienyl cations, seems to occur only to a limited extent. The alicyclic alcohols 22 and 23 (Scheme 18) gave, in Ac₂O/H₂SO₄, as main product the corresponding acetates 73 and 75 , as well as small amounts of olefins 74 and 76 formed by dehydration i.e. [3,4]-rearrangements occur in these systems. Also no [3,4]-rearrangements were observed in solvents reactions of either 4,4-dimethyl-hepta-1, 6-dien-3-yl tosulate (79; see Scheme 19) or its corresponding alcohol 24.     

Modification of 2-trifluoromethyl-1H-benzimidazole with hydroxyalkyl substituents

Alkylation of 2-(trifluoromethyl)-1H-benzimidazole with 4-bromobutyl acetate gave 4-[2-(trifluoromethyl)-1H-benzimidazol-1-yl]butyl acetate which was deacylated by the action of hydrogen chloride in anhydrous ethanol. 4-[2-(Trifluoromethyl)-1H-benzimidazol-1-yl]butan-1-ol thus formed showed a moderate tuberculostatic activity. Alkylation of the title compound with chloromethyloxirane afforded a mixture of 1-chloro-3-[2-(trifluoromethyl)-1H-benzimidazol-1-yl]-propan-2-ol and 1-(oxiran-2-ylmethyl)-2-trifluoromethyl-1H-benzimidazole. A new procedure was proposed for the synthesis of 2-[(2-trifluoromethyl-1Hbenzimidazol-1-yl)methoxy]ethyl acetate.     

Die Dienol-Benzol-Umlagerung von Allyldienolen: aromatische [1,2]-, [3,3]- und [3,4]-sigmatropische Umlagerungen

The dienol-benzene rearrangement of syn and anti-4-allyl-4-methylcyclohexa-2,5-dien-1-ol (syn and anti 15) occurs by formation of a benzonium ion intermediate in p-toluene-sulphonic acid in ether below 0° and leads to a mixture of 2-, 3- and 4-allyltoluenes in the ratio 54:10:36. By the introduction of ¹⁴C-, D- and methyl labelled dienols it is shown that only the allyl group migrates and that this rearrangement is an intramolecular, one-step process. The formation of 2-allyltoluene occurs with retention, whereas the 3- and 4-allyltoluenes are formed by inversion of the carbon skeleton of the migrating allyl group. These rearrangements can be therefore classified as suprafacial, aromatic sigmatropic reactions of the order [1,2], [3,3] and [3,4]. The transition state can be postulated as representing a positively charged complex consisting of interacting allyl and tolyl radicals. The interaction of the two parts is controlled by the symmetry of the highest occupied π-orbitals (ψ₃ for toluene and ψ₂ for the allyl group) in agreement with the Woodward-Hoffmann rules. The better “distribution” of the charge in the transition state of these reactions in comparison to the ground state is chiefly responsible for the CoPE-like [3,3] sigmatropic reaction occurring at low temperatures. In general, sigmatropic reactions in charged systems are faster. The rearrangement of syn and anti 2-allyl-2-methylcyclohexa-3,5-dien-1-ol (syn and anti 28) gives results similar to those obtained with the para-allyldienols. The thermal rearrangement of 15 and 28 gives 3-allyltoluene by a [3,3] sigmatropic Cope rearrangement followed by elimination of water.     

Synthesis of the new ring system,Pyrazolo[3,4-d][1,3]diazepine. A novel route for the synthesis of azolo[1,3]diazepines

A reduction of the nitrile group of 5-amino-4-cyano-1-methylpyrazole ( 3 ) has provided the very versatile compound 5-amino-1-methylpyrazole-4-carboxaldehyde ( 4 ). The amino group of 4 was protected using di-methylformamide dimethylacetal and the aldehyde group was then reacted with trimethylsilyl cyanide to afford the moisture sensitive compound 5-[[(dimethylamino)methylene]amino]-4-[cyano(trimethylsiloxy)-methyl]-1-methylpyrazole ( 10 ). The cyano group of the cyanohydrin 10 was reduced using a cobalt boride catalyst to afford an intermediate aminomethyl group which was involved in an in situ annulation. This reaction provided 1-methyl-1,4,5,6-tetrahydropyrazolo[3,4-d][1,3]diazepin-4-ol, a derivative of the new ring system, pyrazolo[3,4-d][1,3]diazepine.     

Separation of Leucas aspera,a medicinal plant of Bangladesh,guided by prostaglandin inhibitory and antioxidant activities

According to the traditional usage of the plant for antiinflammation and analgesia, Leucas aspera was tested for its prostaglandin (PG) inhibitory and antioxidant activities. The extract showed both activities, i.e., inhibition at 3 x 10(-4) g/ml against PGE(1)- and PGE(2)-induced contractions in guinea pig ileum and a 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect. The separation guided by the activities in these dual assay methods provided eight lignans and four flavonoids, LA-1- -12, among which LA-1- -7 and LA-10- -12 were identified as nectandrin B, meso-dihydroguaiaretic acid, macelignan, acacetin, apigenin 7-O-[6"-O-(p-coumaroyl)-beta-D-glucoside], chrysoeriol, apigenin, erythro-2-(4-allyl-2, 6-dimethoxyphenoxy)-1-(4-hydroxy-3-methoxyphenyl)propan-1-ol, myristargenol B, and machilin C, respectively. LA-8 was determined to be (-)-chicanine, the new antipode of the (+) compound, by spectroscopic methods including CD and ORD. Chiral-HPLC analysis of LA-9 showed that it was a mixture of two enantiomers, (7R, 8R)- and (7S, 8S)-licarin A. All of these components were first isolated from L. aspera. PG inhibition was observed in LA-1, LA-2, and LA-5, and antioxidant activity in LA-1- -3 and LA-8- -12.     

Heterocycles from carbohydrate precursors. Part XIX. The X-ray crystal structure determination of the reaction product of 4-(2-acetoxyethylidene)-4-hydroxy-2,3-dioxobutyro-1,4-lactone-2-(p-bromophenylhydrazone) with methylhydrazine

X-ray crystallographic data show that the product obtained in the reaction of 4-(2-acetoxy-ethylidene)-4-hydroxy-2,3-dioxobutyro-1,4-lactone-2-(p-bromophenylhydrazone) with methyl-hydrazine is the bicyclic compound 2,6-dimethyl-3,4-dioxo-2,3,4,6,7,8-hexahydropyridazino-[4,3-c]pyridazine 4-(p-bromophenylhydrazone) ( 10 ) and not as originally suggested 1-methyl-3-(1-methylpyrazolin-3-yl)-4,5-pyrazoledione 4-(p-bromophenylhydrazone) ( 8 ).     

The synthesis of ventiloquinone L, the monomer of cardinalin 3

Readily available ethyl-4-acetoxy-6,8-dimethoxynaphthalene-2-carboxylate was converted into 1-[3-allyl-4-(benzyloxy)-6,8-dimethoxy-2-naphthyl)-1-ethanol in seven steps. Subjection of this compound to Wacker oxidation conditions provided 5-benzyloxy-7,9-dimethoxy-1,3-dimethyl-1H-benzo[g]isochromene in good yield. Hydrogenation of the isochromene afforded (+/-)-cis-7,9-dimethoxy-1,3-dimethyl-1H-benzo[g]isochroman-5-ol as the major product, which was readily converted into ventiloquinone L.     

Synthesis of new derivatized pyrazole based ligands and their catecholase activity studies

A synthesis of three new tripodal ligands: 3-[bis-(3,5-dimethyl-pyrazol-1-ylmethyl)-amino]-propan-1-ol L1, 3-[bis-(5-methyl-3-carbomethoxy-pyrazol-1-ylmethyl)-amino]-propan-1-ol, L2 and 3-[bis-(5-methyl-3-carboethoxy-pyrazol-1-ylmethyl)-amino]-propan-1-ol L3 is reported. The in situ-generated copper(II) complexes of three new compounds (L1–L3) were examined for their catalytic activities and were found to catalyse the oxidation reaction of catechol to o-quinone with the atmospheric dioxygen. These activities depend on the nature of the ligand and the copper salts.     

New Dolabellane Derivatives from the Brown Alga Dictyota pardalis

Reinvestigation of the brown alga Dictyota pardalis f. pseudohamata CRIBB led to the crystallization of 1 and to the isolation of the two new dolabellane derivatives 2 and 3 . X-Ray analysis of 1 and 2 , together with detailed 1D-and 2D-NMR studies on 2 and 3 , allowed their structures to be elucidated as (1R*,3S*,7S*,11R*,4Z)-dolabella-4,8(17), 12(18)-triene-3,7-diol ( 1 ), (1R*,3S*,4S*,7S*,8S*,11R*,14R*,12E)-3,4:7,8-diepoxydolabe11-12-ene-14, 18-diol ( 2 ), and (1R*,3S*,4S*,7S*,8S*,11R*,14R*)-3,4:7,8-diepoxy-l,4,8,12,12-pentamethylbicyclo[9. 3. 0]tetra-decan-14-ol( 3 ).     

Preparative electroreduction oftrans-2-allyl-6-methyl(phenyl)-1,2,3,6-tetrahydropyridine

Electrocatalytic hydrogenation oftrans-2-allyl-6-phenyl-1,2,3,6-tetrahydropyridine andtrans-2-allyl-6-methyl-1,2,3,6-tetrahydropyridine in 40% aqueous DMF in the presence of AcOH on a nickel cathode gavetrans-6-phenyl-2-propylpiperidine andtrans-2-methyl-6-propylpiperidine ((±)-epidihydropinidine), respectively. Direct electroreduction oftrans-2-allyl-6-phenyl-1,2,3,6-tetrahydropyridine in anhydrous DMF on a mercury cathode afforded a 7 ∶ 5 mixture oftrans- andcis-2-allyl-6-phenylpiperidine. The structure of the latter compound was confirmed by 2D NOESY spectroscopy. The possible mechanism of formation of thecis-isomer is discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No.4, pp. 758–761, April, 1999.     

Synthesis and antimalarial effects of 2-(3,4-dichloroanilino)-7-[[[(dialkylamino)alkyl]amino]]-5-methyl-s-triazolo[1,5-a]pyrimidines

3,4-Dichlorophenylisothioeyanate ( 10 ) was allowed to react with 2-methy1-2-thiopseudourea to give methyl 4-(3,4-dichlorophenyl)(dithioaltophanimidate ( 11 ) (41%), which upon treatment with hydrazine afforded 3-amino-5-(3,4-dichloroanilino)-s-triazole ( 12 ) (54-91%). Ring-closure with ethyl acetoacetale in acetic acid afforded 2-(3,4-dichloroanilino)-5-methyl-s-triazolo[ 1,5-α ]-pyrimidin-7-ol ( 13 ) (81%). Chlorination with phosphorus oxychloride gave 7-chloro-2-(3,4-dichloroanilino)-5-methyl-s-triazolo[1,5-α ]pyrimidine ( 14 ) (98%), which was condensed with various amines to yield the desired 2-(3,4-diehloroanilino)-7-¶[(dialkylamino)alkyl]arnino¶-5-methyl-s-triazolo[ 1,5-α]pyrimidines ( 6 a-d). The structures of the s-triazolo[ 1,5-α ]pyrimidines were based on nmr spectroscopy and ring stability considerations. Several of the amino-s-triazolo[ 1,5-α ]pyrimidines possessed antimalarial activity against P. berghei in mice.