Protective group-free syntheses of (±)-frontalin, (±)-endo-brevicomin, (±)-exo-brevicomin, and (±)-3,4-dehydro-exo-brevicomin: racemic pheromones with a 6,8-dioxabicyclo[3.2.1]octane ring

Protective group-free syntheses of four racemic pheromones with a 6,8-dioxabicyclo[3.2.1]octane ring were achieved in five or six steps from commercially available (±)-3-butyn-2-ol (6) and 2-alkenyl halides or 2-alken-1-ol by employing Lewis acid-catalyzed acetalization of δ, ε-epoxy ketones as the key reaction. (±)-Frontalin (1) was prepared in a 25% overall yield in five steps from methallyl chloride (5a), (±)-endo-brevicomin (2) was prepared in a 23% overall yield in five steps from (E)-2-pentenyl bromide (5b), and (±)-exo-brevicomin (3) and (±)-3,4-dehydro-exo-brevicomin (4) were both prepared in a 4% overall yield in six steps based on (Z)-2-penten-1-ol (12).     

Large-scale preparation of (9Z,12E)-[1-(13)C]-octadeca-9,12-dienoic acid, (9Z,12Z,15E)-[1-(13)C]-octadeca-9,12,15-trienoic acid and their [1-(13)C] all-cis isomers

Several grams of labelled trans linoleic and linolenic acids with high chemical and isomeric purities (>97%) have been prepared for human metabolism studies. A total of 12.5 g of (9Z, 12E)-[1-(13)C]-octadeca-9,12-dienoic acid and 6.3 g of (9Z,12Z, 15E)-[1-(13)C]-octadeca-9,12,15-trienoic acid were obtained in, respectively, seven steps (7.8% overall yield) and 11 steps (7% overall yield) from 7-bromo-heptan-1-ol. The trans bromo precursors used for the labelling were synthesised by using copper-catalysed couplings. The trans fatty acids were then obtained via the nitrile derivatives. A total of 23.5 g of (9Z,12Z)-[1-(13)C]-octadeca-9, 12-dienoic acid and 10.4 g of (9Z,12Z,15Z)-[1-(13)C]-octadeca-9,12, 15-trienoic acid were prepared in five steps in, respectively, 32 and 18% overall yield. Large quantities of bromo and chloro precursors were synthesised from the commercially available acid according to Barton's procedure. In all cases, the main impurities (>0.5%) of each labelled fatty acid have been characterised.     

Chiral synthesis of (2S,3S)-2-(2-morpholin-2-yl-2-phenylmethoxy)phenol

Resolution of (2RS,3RS)-2-[alpha-(2-methoxymethoxyphenoxy)phenylmethyl]morpholine, 11, with (+) mandelic acid led to the formation of (+)-(2S,3S)-2-[alpha-(2-methoxymethoxyphenoxy)phenyl methyl] morpholine (11a). Compound 11 was synthesized in seven steps from (2RS,3RS)-cinnamyl alcohol-2,3-epoxide (4), with an overall yield of 17%. Cleavage of the methoxymethyl group of the Fmoc derivative 12 with catalytic amounts of p-toluenesulfonic acid in methanol afforded (+)-(2S,3S)-2-(2-morpholin-2-yl-2-phenylmethoxy)phenol 2. The synthetic utility as well as the configuration of compound 2 has been demonstrated by converting (S,S)-2-(2-morpholin-2-yl-2-phenylmethoxy)phenol 2 to (2S,3S)-2-[alpha-(2-ethoxyphenoxy)phenylmethyl]morpholine (1) and (2S,3S)-2-(2-methoxyphenoxy) benzyl)morpholine (16), two potential norepinephrine reuptake inhibitors under clinical evaluation.     

Total synthesis of (+)-albicanol and (+)-albicanyl acetate.

The drimane sesquiterpenes, (+)-albicanol (2) and (+)-albicanyl acetate (3), were synthesized from an optically active bicyclic diol [(+)-1] that had been obtained via the recently developed optical resolution of a general synthetic intermediate for drimane sesquiterpenes. The crucial step in the previous syntheses was markedly improved by the modified Wittig methylenation of a silyloxy ketone (7). The high overall yield (77% in 4 or 5 steps from (+)-1) by this total synthesis makes it possible to synthesize the other biologically active drimane sesquiterpenes.     

(+)-12alpha-Hydroxysophocarpine, a new quinolizidine alkaloid and related anti-HBV alkaloids from Sophora flavescens

(+)-12alpha-Hydroxysophocarpine (8), a new quinolizidine alkaloid was isolated from the roots of Sophora flavescens, together with 10 known quinolizidine alkaloids, (+)-oxymatrine (1), (+)-matrine (2), (+)-9alpha-hydroxymatrine (3), (+)-allomatrine (4), (+)-oxysophocarpine (5), (-)-sophocarpine (6), (-)-9alpha-hydroxysophocarpine (7), (+)-lehmannine (9), (-)-13,14-dehydrosophoridine (10), and (-)-anagyrine (11). Their structures were elucidated by spectroscopic methods, and the stereochemistry of 8 was confirmed by X-ray analysis. These alkaloids were tested for anti-hepatitis B virus (HBV) activity in vitro, compounds 5, 6, 9, and 10 showed significant anti-HBV activity with inhibitory potency against HBsAg secretion at 48.3-79.3% and that against HBeAg secretion at 24.6-34.6%.     

Intramolecular reductive cyclization strategy to the synthesis of (-)-6-methyl-3-hydroxy-piperidine-2-carboxylic acid, (+)-6-methyl-(2-hydroxymethyl)-piperidine-3-ol and their glycosidase inhibitory activity

The first stereoselective synthesis of (2S,3R,6S)-6-methyl-3-hydroxy-piperidine-2-carboxylic acid (-)-6 and (2R,3R,6S)-6-methyl-(2-hydroxymethyl)-piperidine-3-ol (+)-7 was achieved starting from readily available d-glucose in 14 steps with 17% overall yield for both the compounds. The key feature of the present strategy includes the Wittig-olefination for the preparation of required conjugated keto-azide 9 and construction of 2,3,6-trisubstituted piperidine skeleton 11 by applying intramolecular reductive cyclization of conjugated keto-azide intermediate. The glycosidase inhibitory activity of compounds 6 and 7 towards several glycosidases has been evaluated.     

Synthesis and biological activity of 2-aminopurine methylenecyclopropane analogues of nucleosides

Synthesis and biological activity of racemic 2-aminopurine methylenecyclopropane analogues of nucleosides 4, 5, 10 and 11 is described. One-pot alkylation-elimination of 2-aminopurine (6) with dibromide 7 gave a mixture of four isomeric methylenecyclopropanes. The (E, Z)-N9 and (E, Z)-N7 isomers 8 and 9 were resolved by chromatography on silica gel. Deacetylation of 8 afforded the respective (Z)-N9 and (E)-N9 isomers 4 and 10 which were separated by chromatography on silica gel. In a similar fashion, (E, Z)-N7 mixture 9 furnished (Z)-N7 and (E)-N7 isomers 5 and 11. The S-(+)-enantiomer 4 was obtained by desulfurization of (S)-(+)-6-thiosynguanol (13) with Raney Ni. Compound 13 was obtained from (S)-(+)-2-amino-6-chloro derivative 12 and NaSH in methanol. Racemic analogues 4, 5, 10 and 11 were inactive against HCMV, HSV-1, HSV-2, EBV and VZV. Enantiomer (S)-(+)-4 inhibited replication of HSV-1 in BSC-1 cells (ELISA) with EC50 35 microM and it was non-cytotoxic in KB cells (CC50 > 100 microM). Compound (S)-(+)-4 was also moderately effective against VZV in HFF culture with EC50/CC50 (microM) 60/>460 and it was a substrate for xanthine oxidase.     

Synthesis of polyhydroxysterols (III): synthesis and structural elucidation of 24-methylenecholest-4-en-3beta,6 alpha-diol

Using stigmasterol as the starting material, 24-methylenecholest-4-en-3beta,6 alpha-diol (2) was synthesized in eight steps in 13% overall yield. The introduction of the sterol side-chain was carried out using (3-methyl-2-oxobutyl)-triphenylarsonium bromide (11) and K(2)CO(3) in a solid-liquid phase-transfer Wittig reaction. Construction of the steroidal nucleus was finished by oxidation of 24-methylenecholest-5-en-3beta-ol (9) with pyridinium chlorochromate (PCC) in dichloromethane at ambient temperature and by reduction of 24-methylenecholest-4-en-3,6-dione (10) with NaBH(4) in the presence of CeCl(3).7H(2)O.     

Volatile components from European liverworts Marsupella emarginata,M. aquatica and M. alpina

The hydrodistillation products of the liverworts Marsupella emarginata, M. aquatica and M. alpina were investigated by spectroscopic methods. A number of new compounds could be isolated by preparative gas chromatography (GC) and identified by spectroscopic techniques including GC-mass spectrometry, NMR and chemical correlations in conjunction with enantioselective GC. From M. emarginata, in addition to many known compounds, the sesquiterpene hydrocarbon (-)-7-epi-eremophila-1(10),8,11-triene (1) and the sesquiterpene derivatives (-)-4-epi-marsupellol (2), (-)-marsupellol acetate (18), (-)-4-epi-marsupellol acetate (4), (+)-5-hydroxymarsupellol acetate (5) and (-)-9-acetoxygymnomitr-8(12)-ene (24) could be identified. In M. aquatica the sesquiterpene hydrocarbons (-)-myltayl-8(12)-ene (7), ent-(+)-amorpha-4,11-diene (8), (-)-amorpha-4,7(11)-diene (9), the sesquiterpene alcohol (+)-9-hydroxyselina-4,11-diene (10) and (-)-2-acetoxyamorpha-4,7(11)-diene (11) were identified. In M. alpina (-)-trans-selina-4(15),11-dien-5-ol (12), (+)-8,9-epoxyselina-4,11-diene (13) and (+)-cis-selina-4(15),11-dien-5-ol (14) were found as new natural products.     

Synthesis of [O-methyl-11C]1-(2-chlorophenyl)-5-(4-methoxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide: a potential PET ligand for CB1 receptors

Synthesis and in vitro evaluation of [O-methyl-(11)C]1-(2-chlorophenyl)-5-(4-methoxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide ([(11)C]-1), a potential imaging agent for CB(1) receptors using PET is described. 1-(2-Chlorophenyl)-5-(4-hydroxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide (5), the precursor for radiolabeling, was synthesized from 4-OTBDPS-propiophenone (2) in five steps with 30% overall yield. The reaction of alcohol 5 with [(11)C]MeOTf at 60 degrees C afforded [(11)C]-1 with an average radiochemical yield of 14.5% (EOS) and >2000 Ci/mmol specific activity. The radiotracer was found to selectively label CB(1) receptors in slide-mounted sections of postmortem human brain containing prefrontal cortex as demonstrated by in vitro autoradiography using phosphor imaging.     

The first synthesis of [11C]J147, a new potential PET agent for imaging of Alzheimer’s disease

J147 was synthesized from 2,4-dimethylphenylhydrazine hydrochloride and 3-methoxybenzaldehyde in 2 steps with 71% overall yield. The precursor desmethyl-J147 was synthesized from 3-hydroxybenzaldehyde and 2,4-dimethylphenylhydrazine hydrochloride in 4 steps with 63% overall yield. [¹¹C]J147 was prepared from desmethyl-J147 with [¹¹C]CH₃OTf through O-[¹¹C]methylation and isolated by HPLC combined with solid-phase extraction (SPE) in 35–50% radiochemical yield based on [¹¹C]CO₂ and decay corrected to end of bombardment (EOB), with 370–740 GBq/μmol specific activity at EOB.     

Sequential substitution of 1,2-dichloro-ethene: a convenient stereoselective route to (9Z,11E)-, (10E,12Z)- and (10Z,12Z)-

Conjugated linoleic acid (CLA) isomers are present in human foods derived from milk or ruminant meat. To study their metabolism, (9Z,11E)-, (10E,12Z)- and (10Z,12Z)-[1-(14)C]-octadecadienoic acids with high radiochemical and isomeric purities (>98%) were prepared by stereoselective multi-step syntheses involving sequential substitution of 1,2-dichloro-ethene. In the case of the (9Z,11E) isomer, a first metal-catalyzed cross-coupling reaction between (E)-1,2-dichloro-ethene and 2-non-8-ynyloxy-tetrahydro-pyran, obtained from 7-bromo-heptan-1-ol, gave a conjugated chloroenyne. A second coupling reaction with hexylmagnesium bromide provided a heptadecenynyl derivative. Stereoselective reduction of the triple bond and bromination afforded (7E,9Z)-17-bromo-heptadeca-7,9-diene. Formation of the Grignard reagent and carbonation with 14CO(2) gave (9Z,11E)-[1-(14)C]-octadeca-9,11-dienoic acid (overall yield from 7-bromo-heptan-1-ol, 14.4%). (10E,12Z)- and (10Z,12Z)-[1-(14)C]-octadeca-10,12-dienoic acids were synthesized by the same methodology using 1-heptyne, 8-bromo-octan-1-ol and, respectively, (E)-1,2-dichloro-ethene and its (Z) isomer (overall yield from 8-bromo-octan-1-ol, 13.1% (10E,12Z); 17.2% (10Z,12Z)). Impurities (<2% if present) were identified as being (E,E) CLA isomers and were removed by RP-HPLC. Metabolism studies in animal are in progress.     

Galabiosyl donors; efficient synthesis from 1,2,3,4, 6-penta-O-acetyl-beta-D-galactopyranose

1,2,3,4,6-Penta-O-acetyl-beta-D-galactopyranose was transformed into phenyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-galactopyranoside (5) and 4-methoxyphenyl 2,3,6-tri-O-benzoyl-beta-D-galactopyranoside (8) in 73% (two steps) and 58% (three steps) yield, respectively. Glycosylation of the acceptor 8 with donor 5 using N-iodosuccinimide-trimethylsilyl trifluoromethanesulfonate as promoter furnished the galabioside 9 (8.8 g) in 95% yield. Further transformations provided in high yields anomerically-activated galabiosides (thioglycoside (1), trichloroacetimidate (2), and bromosugar (3)) suitable for use as glycosyl donors in syntheses of galabiose-containing oligosaccharides. Several of the compounds reported here are crystalline, which greatly simplified purifications.     

Microbial transformation of (+)-nootkatone and the antiproliferative activity of its metabolites

Six metabolites were obtained as a result of microbial transformation of (+)-nootkatone (1) by the fungal strains: Botrytis, Didymosphaeria, Aspergillus, Chaetomium and Fusarium. Their structure were established as (+)-(4R,5S,7R,9R)-9α-hydroxynootkatone (2), (+)-(4R,5S,7R)-13-hydroxynootkatone (3) and (+)-(4R,5S,7R,9R,11S)-11,12-epoxy-9α-hydroxynootkatone (4), (+)-(4R,5S,7R,11S)-11,12-epoksynootkatone (5), (+)-(4R,5S,7R)-11,12-dihydroxynootkatone (6) and (+)-(4R,5S,7R)-7,11,12-trihydroxynootkatone (7) on the basis of their spectral data. Two products: (4) and (7) were not previously reported in the literature. The antiproliferative activity of (+)-nootkatone (1) and isolated metabolites (2-7) of its biotransformation has been evaluated.     

Metathesis-mediated synthesis of (R)-10-methyl-2-tridecanone, the southern corn rootworm pheromone

(R)-10-Methyl-2-tridecanone, the female sex pheromone of the southern corn rootworm (Diabrotica undecimpunctata howardi Barber), was synthesized in 9 steps from methyl (S)-3-hydroxy-2-methylpropanoate in a 15.7% overall yield. Olefin cross metathesis between (R)-6-methyl-1-nonene and 5-hexen-2-one employing Grubbs' first-generation catalyst was the key step of the synthesis.     

Synthesis and antiviral properties of some polyphenols related to Salvia genus

An efficient synthesis of the acid part of salvianolic acid E 2 is described. Compound 2 was obtained from vanillin in 10 steps and 21% overall yield. During the synthesis of 2 an unexpected 5-oxo-4b,9b-dihydroindano[1,2-b]benzofuran rac-12 was isolated. Both compounds together with the acid part of salvianolic acid D were active as HIV-1 integrase inhibitors at the submicromolar level. But they did not inhibit the replication of the virus on MT-4 cells.     

Development and optimization of fractional precipitation for the pre-purification of (+)-dihydromyricetin

A novel fractional precipitation process, both simple and efficient, was developed for producing (+)-dihydromyricetin in high purity and high yield from crude extracts. The optimal acetone composition in water, initial (+)-dihydromyricetin concentration in crude extract, storage temperature, storage time, and pH were 1/5 (v/v), 0.1 g/mL, 4°C, 32 h, and 9.0, respectively. Crude extracts were efficiently pre-purified using fractional precipitation of (+)-dihydromyricetin by differences of solubility in an acetone solution, increasing purity from 55.0 to over 84.9% with an overall yield of 97.5%. The use of fractional precipitation for pre-purification allowed for rapid and efficient separation of (+)-dihydromyricetin from interfering compounds and dramatically increased the purity of crude (+)-dihydromyricetin for subsequent purification steps.     

Free radical oxidation of coriolic acid (13-(S)-hydroxy-9Z,11E-octadecadienoic acid)

The reaction of (13S,9Z,11E)-13-hydroxy-9,11-octadecadienoic acid (1a), one of the major peroxidation products of linoleic acid and an important physiological mediator, with the Fenton reagent (Fe(2+)/EDTA/H(2)O(2)) was investigated. In phosphate buffer, pH 7.4, the reaction proceeded with >80% substrate consumption after 4h to give a defined pattern of products, the major of which were isolated as methyl esters and were subjected to complete spectral characterization. The less polar product was identified as (9Z,11E)-13-oxo-9,11-octadecadienoate (2) methyl ester (40% yield). Based on 2D NMR analysis the other two major products were formulated as (11E)-9,10-epoxy-13-hydroxy-11-octadecenoate (3) methyl ester (15% yield) and (10E)-9-hydroxy-13-oxo-10-octadecenoate (4) methyl ester (10% yield). Mechanistic experiments, including deuterium labeling, were consistent with a free radical oxidation pathway involving as the primary event H-atom abstraction at C-13, as inferred from loss of the original S configuration in the reaction products. Overall, these results provide the first insight into the products formed by oxidation of 1a with the Fenton reagent, and hint at novel formation pathways of the hydroxyepoxide 3 and hydroxyketone 4 of potential (patho)physiological relevance in settings of oxidative stress.     

A preparative synthesis of 3-amino-2,3,6-trideoxy-L-lyxo-hexose (daunosamine) hydrochloride from D-mannose.

A simple, preparative route in nine steps from methyl alpha-D-mannopyranoside (1) is described that affords, in 40% overall yield, the title amino sugar 11, the sugar constituent of the antitumor antibiotics adriamycin and daunorubicin. The 2,3:4,5-dibenzylidene acetal (2) of 1 is converted by butyllithium into the 2-deoxy-3-ketone 3, whose oxime 4 is reduced with high stereoselectivity to the D-ribo amine, isolated as its N-acetyl derivative 5 and converted by action of N-bromosuccinimide into the 4-O-benzoyl-6-bromide 7. Dehydrohalogenation of gives the 5,6-unsaturated glycoside 8, which, after O-debenzoylation to 9, undergoes stereospecific reduction by hydrogen with net C-5 inversion to give the crystalline, N-acetylated methyl beta-glycoside (10) of daunosamine, readily converted into daunosamine hydrochloride (11) and into the crystalline N-benzoyl (14) and N-acetyl(15) derivatives. No chromatographic procedures for isolation are required in any of the steps.     

Synthesis of polyhydroxysterols (I): synthesis of 24-methylenecholest-4-en-3beta,6beta-diol, a cytotoxic natural hydroxylated sterol

Starting from stigmasterol (2), 24-methylenecholest-4-en-3beta, 6beta-diol (1), a cytotoxic natural dihydroxylated sterol, was synthesized via 10 steps in 20% overall yield. The introduction of a side-chain of sterol was achieved by solid-liquid phase-transfer Wittig reaction using (3-methyl-2-oxo)butyltriphenylarsonium bromide (12) and K(2)CO(3). Construction of the steroidal nucleus was finished by the addition of 3beta-acetoxycholest-5,6-en-24-one (7) with NBA in dioxane under ambient temperature and by the elimination of 3beta, 6beta-diacetoxy-5a-bromocholestane-24-one (9). The spectral data of the synthetic product (1) are completely consistent with those of the natural compound (1).