(−)-Epilamprolobine and its N-oxide,lupin alkaloids from Sophora tomentosa

From the fresh leaves of Sophora tomentosa, three new lupin alkaloids, (?)-epilamprolobine, (+)-epilamprolobine N-oxide and 5-(3′-methoxycarbonylbutyroyl)aminomethyl-trans-quinolizidine N-oxide, have further been isolated along with (+)-matrine, (+)-matrine N-oxide, (+)-sophocarpine N-oxide, (?)-anagyrine, (?)- baptifoline, (?)-cytisine, (?)-N-methylcytisine, (?)-N-formylcytisine, (?)-N-acetylcytisine and (±)-ammodendrine. The absolute configurations of (+)-epilamprolobine N-oxide (1R:5R:6S) and (?)-epilamprolobine (5R:6S) have also been established by spectroscopic data and by comparison with synthetic (+)-epilamprolobine (5S:6R)derived from (?)-lupinine (5R:6R). (?)-Epilamprolobine is a diastereomer of (+)-lamprolobine (5R:6R) in Lamprolobium fruticosum and 5-(3′-methoxycarbonylbutyroyl) aminomethyl-trans-quinolizidine N-oxide is presumed to be an artefact. A biosynthetic pathway for the formation of (?)-epilamprolobine is also proposed.     

Formation of (-⊃-1′,2′-epi-2-cis-xanthoxin acid from a precursor of abscisic acid

Tomato shoots and avocado mesocarp supplied with (±)-[2-¹⁴C]-5-(1,2-epoxy-2,6,6-trimethylcyclohexyl)-3-methylpenta-cis-2-trans-4-dienoic acid metabolize it into (+)-abscisic acid and a more polar material that was isolated and identified as (?)-epi-1′(R),2′(R)-4′(S)-2-cis-xanthoxin acid. The (+)-1′(S),2′(S)-4′(S)-2-cis-xanthoxin acid recently synthesized from natural violaxanthin, has the 1′,2′-epoxy group on the opposite side of the ring to that of the 4′(S)-hydroxyl group and the compound is rapidly converted into (+)-abscisic acid. The 1′,2′-epoxy group of (?)-1′,2′-epi-2-cis-xanthoxin acid is on the same side of the ring as the 4′(S) hydroxyl group: the compound is not metabolized into abscisic acid. The configuration of the 1′,2′-epoxy group probably controls whether or not the 4′(S) hydroxyl group can be oxidized. (+)-2-cis-Xanthoxin acid is probably not a naturally occurring intermediate because a ‘cold trap’, added to avocado fruit forming [¹⁴C]-labelled abscisic acid from [2-¹⁴C]mevalonate, failed to retain [¹⁴C] label.     

Biosynthesis of the bisbenzylisoquinoline alkaloid,tetrandrine

The incorporation of (±)-coclaurine, (±)-norcoclaurine, (±)-N-methylcoclaurine and didehydro-N-methyleoclaurinium iodide into tetrandrine in Cocculus laurifolius has been studied and specific utilization of (±)-N-ethylcoclaurine demonstrated. The evidence indicates that tetrandrine is formed in the plants by oxidative dimerization of N-methylcoclaurine. Double labelling experiment with (±)-N- [¹⁴C]-methyl- [1-³H]-coclaurine demonstrated that the hydrogen atom at the asymmetric centre in the 1-benzylisoquinoline precursor is retained in the bioconversion into tetrandrine. Parallel feedings of (+)-(S)- and (?)-(R)-N-methylcoclaurines showed that the stereospecificity is maintained in the biosynthesis of tetrandrine from the 1-benzylisoquinoline precursor.     

Synthesis of (+)-(R)- and (−)-(S)-trans-8-hydroxy-2-[N-n-propyl-N-(3′-iodo-2′-propenyl)] aminotetralin: New 5-HT1A receptor ligands

(R,S)-trans-8-Hydroxy-2-[N-n-propyl-N-(3′-iodo-2′-propenyl)amino]tetralin 7 , a new radioiodinated ligand based on 8-OH-DPAT, was reported as a potential ligand for 5-HT_1A receptors. The optically active (+)-(R)- and (?)-(S)- 7 were prepared to investigate the stereoselectivity of (R,S)- 7 . Racemic intermediate 8-methoxy-2-N-n-propyltetralin was reacted with the acyl chloride of (?)-(R)-O-methylmandelic acid to form a mixture of (S,R)- and (R,R)-diastereoisomers, which were separated by flash column chromatography. After removing the N-acyl group from the diastereoisomers, the desired (+)-(R)-or (?)-(S)- 7 was obtained by adding an N-iodopropenyl group. In vitro homogenate binding studies showed the stereoselectivity of this new compound for 5-HT_1A receptors. (+)-(R)- 7 isomer displayed 100-fold higher affinity than the (?)-(S)- 7 isomer. Biochemical study indicated that (+)-(R)- 7 potently inhibited forskolin-stimulated adenylyl cyclase activity in hippocampal membranes (E_max and EC₅₀ were 24.5% and 5.4 nM, respectively), while (?)-(S)- 7 showed no effect at 1 μM. The radioiodinated (+)-(R)- and (?)-(S)-[¹²⁵I] 7 were confirmed by coelution with the resolved unlabeled compound on HPLC (reverse phase column PRP-1, acetonitrile/pH 7.0 buffer, 80/20). The active isomer, (+)-(R)-[¹²⁵I] 7 , displayed high binding affinity to 5-HT_1A receptors (K_d = 0.09 ± 0.02 nM). In contrast, the (?)-(S)- 7 isomer displayed a significantly lower affinity to the 5-HT_1A receptor (K_d > 10 nM). Thus, (+)-(R)-[¹²⁵I]trans-8-OH-PIPAT, (+)-(R)- 7 , an iodinated stereoselective 5-HT_1A receptor agonist, is potentially useful for study of in vivo and in vitro function and pharmacology of 5-HT_1A receptors in the central nervous system. © 1995 Wiley-Liss, Inc.     

Usnic acid derivatives from Leprocaulon microscopicum

In addition to known dibenzofuran derivatives such as (?)-usnic acid, (?)-isousnic acid and (?)-placodiolic acid, a Leprocaulon microscopicum acetone extract yielded a new compound, (±)-9-O-methylplacodiolic acid in a keto-enol equilibrium focused on the C-ring. Structures were established using mass spectrometry and combination of 1D and 2D NMR spectral data. ¹³C assignments of placodiolic acid were revised. Tautomers of the (±)-9-O-methylplacodiolic acid were only separated by GC and a thorough fragmentation study confirmed the structural features. To complete the study, evaluation of antiproliferative effects on HT-29 human colorectal cancer cells showed moderate activity for (?)-usnic acid only.     

Alkaloids of Thermopsis Lupinoides

Ammodendrine, together with seven other known lupin alkaloids, was isolated from Thermopsis lupinoides. (+)-Lupanine (+)-17-oxolupanine occurred together with (?)anagyrine, (?)-baptifoline, (?)-cytisine, (?)-N-methylcytisine (?)N-formylcytisine. These alkaloids have the opposite stereochemistry to that of (+)-lupanine and (+)-17-oxolupanine. The distribution of alkaloids in fresh flowers, leaves, stems roots of this plant was also examined.     

Stereochemistry of tropane alkaloid formation in Datura

Five-month-old Datura innoxia plants were fed via the roots with either d(+)-hygrine-[2′-¹⁴C] or l(?)-hygrine-[2′-¹⁴C]. After 7 days the root alkaloids 3α,6β-ditigloyloxytropane, 3α,6β-ditigloyloxytropan-7β-ol, hyoscine, hyoscyamine and cuscohygrine were isolated from both groups of plants. d(+) but not l(?)-hygrine acts as a precursor for the tropane alkaloids whereas both enantiomers appeared to serve equally well in the biosynthesis of cuscohygrine.     

The preparation of high specific activity [3H]chloramphenicol base and chloramphenicol labeled in the propanediol side chain

Methods are described for the synthesis of [³H]chloramphenicol and derivatives labeled on carbon 1 of the propanediol side chain, with a specific activity of about 2 mCi/μmol. The labeling step involves the reduction of the I-oxo derivative of N-acetyl chloramphenicol base by KB³H₄ to produce a mixture of the d (?) threo- and d (?) erythro-diastereoisomers, since carbon 1 is an asymmetric carbon atom. The two isomers were separated by thin-layer chromatography after acetylation of the two free hydroxyls. After hydrolysis of the three acetyl groups, the biologically active d (?) threo-[1 ? ³H]chloramphenicol base was converted to chloramphenicol. Modification of the above procedures allows the rapid and simple preparation of the mixed d (?) threo- and d (?) erythro-isomers of [1 ? ³H]chloramphenicol. This mixture can be used where the presence of the inactive d (?) erythro-isomer of chloramphenicol is not important. The modified procedure also allows the preparation of the mixed isomers of [1 ? ³H]chloramphenicol base and of chloramphenicol analogs. Attempts to prepare a 3-aldehyde derivative of chloramphenicol were not successful. If this could be done, reduction of this derivative with KB³H₄ would produce the correct isomer of chloramphenicol since carbon atom 3 on the propanediol side chain is not an asymmetric carbon atom.     

Behavioral comparisons of the stereoisomers of tetrahydrocannabinols

The potencies of (?)-$\text{trans}$-Δ⁹-THC, (+)-$\text{trans}$-Δ⁹-THC, (+)-$\text{cis}$-Δ⁹-THC, (?)-$\text{trans}$-Δ⁸-THC and (+)-$\text{trans}$-Δ⁸-THC were compared in several different species. (?)-$\text{trans}$-Δ⁹-THC was 100 times more potent than (+)-$\text{trans}$-Δ⁹-THC in depressing schedule-controlled responding in monkeys. The (+)-$\text{trans}$ isomers were less effective than their corresponding (?)-$\text{trans}$ isomers in the dog static-ataxia test, but potency ratios could not be determined due to a lack of dose-responsiveness of the (+)-$\text{trans}$ isomers. However, it appeared that their potency differed by at least ten fold. The potency of (+)-$\text{cis}$-Δ⁹-THC in the dog static-ataxia test was comparable to that of (+)-$\text{trans}$-Δ⁹-THC. The hypothermia in mice produced by the (?) isomers of $\text{trans}$-Δ⁹-THC and $\text{trans}$-Δ⁸-THC were 9.1 and 30.4 times greater than that produced by their respective (+)-isomers. Also, the potency ratio of the (+)- and (?)-$\text{trans}$-Δ⁹-THC was 5.6 as measured by depression of spontaneous activity in mice. The magnitude of the potency ratios of the THC stereo-isomers is dependent upon the species and the pharmacological test used.     

Biosynthesis of pisatin: Experiments with enantiomeric precursors

Feeding experiments in cupric chloride-treated Pisum sativum pods and seedlings have demonstrated the preferential incorporation of (+)-(6aS,11aS)-[³H]maackiain over (?)-(6aR, 11aR)-[¹⁴C]maackiain into (+)-(6aR, 11aR)-pisatin, establishing that the 6a-hydroxylation of pterocarpans proceeds with retention of configuration. (+)- (6aR,11aR)-6a-hydroxymaackiain was similarly incorporated much better than (?)-(6aS,11aS)-6a- hydroxymaackiain. Where (?)-isomers were incorporated, optical activity measurements on the pisatin produced indicated significant synthesis of (?)-pisatin as well as the normal (+)-pisatin. 7,2′-Dihydroxy-4′,5′- methylenedioxyisoflav-3-ene and both enantiomers of 7,2′-dihydroxy-4′,5′-methylenedioxyisoflavan were poor precursors of pisatin.     

The use of a tritium release assay to measure 6-N-trimethyl-L-lysine hydroxylase activity: synthesis of 6-N-[3-3H]trimethyl-DL-lysine

6-N-[3-³H]Trimethyl-dl-lysine was synthesized from 6-N-acetyl-l-lysine by the following chemical scheme: 6-N-acetyl-l-lysine → 2-keto-6-N-acetylcaproic acid → 2-[3-³H]keto-6-N-acetylcaproic acid → 2-[3-³H]keto-6-N-acetylcaproic acid oxime → 6-N-[3-³H]acetyl-dl-lysine → dl-[3-³H]lysine → 2-N-[3-³H]formyl-dl-lysine → 2-[3-³H]formyl-6-N-trimethyl-dl-lysine → 6-N-[3-³H]trimethyl-dl-lysine. Using a 70% ammonium sulfate fraction obtained from a high-speed rat kidney supernatant, the cosubstrate and cofactor requirements for 6-N-trimethyl-l-lysine hydroxylase activity as measured by tritium release from 6-N-[3-³H]trimethyl-dl-lysine were: α-ketoglutarate, ferrous ions, l-ascorbate, and oxygen, with added catalase showing a slight but distinct stimulatory effect. On incubation with the crude rat kidney preparation, the release of tritium from 6-N-[3-³H]trimethyl-dl-lysine was linear with both time of incubation and protein concentration. Hydroxylation of 6-N-trimethyl-l-lysine, as measured by tritium release from the labeled substrate, was examined in rat kidney, heart, liver, and skeletal muscle tissues, and found to be most active in the kidney.     

Synthesis and Enantioselectivity of Cyclopropavir Phosphates for Cellular GMP Kinase

Enantiomeric cyclopropavir phosphates (+)-9 and (?)-9 were synthesized and investigated as substrates for GMP kinase. N²-Isobutyryl-di-O-acetylcyclopropavir (11) was converted to (+)-monoacetate 12 using hydrolysis catalyzed by porcine liver esterase. Phosphorylation via phosphite 13 gave after deacylation, phosphate (+)-9. Acid-catalyzed tetrahydropyranylation of (+)-monoacetate 12 gave, after deacylation, tetrahydropyranyl derivative 14. Phosphorylation via phosphite 15 furnished, after deprotection, enantiomeric phosphate (-)-9. Racemic diphosphate 16 was also synthesized. The phosphate (+)-9 is a relatively good substrate for GMP kinase with a K_M value of 57 μM that is similar to that of the natural substrates GMP (61 μM) and dGMP (82 μM). In contrast, the enantiomer (?)-9 is not a good substrate (K_M 1200 μM) indicating a significant enantioselectivity for the GMP kinase catalyzed reaction of monophosphate to diphosphate.     

Synthesis, characterization and antimalarial activity of new chromium arene-quinoline half sandwich complexes

Organometallic analogs of chloroquine (CQ) are of interest as drug candidates that may be able to overcome the widespread chloroquine resistance developed by malaria parasites. Two new chromium arene CQ-analogs: [η⁶-N-(7-chloroquinolin-4-yl)-N′-(2-dimethylamino-methylbenzyl)-ethane-1,2-diamine]tricarbonylchromium 4 and [η⁶-N-(7-chloroquinolin-4-yl)-N′-(2-dimethylaminobenzyl)-ethane-1,2-diamine]tricarbonylchromium 9 have been synthesized and characterized. In addition, X-ray crystal structures of the intermediates (η⁶-benzyldimethylamine)tricarbonylchromium 2, [η⁶-2-((dimethylamino)methyl) benzaldehyde]tricarbonylchromium 3 and p-(η⁶-dimethylaminobenzaldehyde)tricarbonyl chromium 8 are reported. Compound 4 was more active than chloroquine against both CQ-sensitive and CQ-resistant strains of Plasmodium falciparum when antimalarial activity was tested in vitro. The activity of 4 against the CQ-resistant parasite strain was twice as high as for the organic ligand alone (IC₅₀ values of 33.9 nM versus 63.1 nM).     

Biosynthesis of (+)-Tartaric Acid from l-[4-C]Ascorbic Acid in Grape and Geranium

The metabolic fate of l-[4-¹⁴C]ascorbic acid has been examined in the grape (Vitis labrusca L.) and lemon geranium (Pelargonium crispum L. L'Hér. cv. Prince Rupert) under conditions comparable to data from l-[1-¹⁴C]ascorbic acid and l-[6-¹⁴C]ascorbic acid experiments. In detached grape leaves and immature berries, l-[4-¹⁴C]ascorbic acid and l-[1-¹⁴C]ascorbic acid were equivalent precursors to carboxyl labeled (+)-tartaric acid. In geranium apices, l-[4-¹⁴C]ascorbic acid yielded internal labeled (+)-tartaric acid while l-[6-¹⁴C]ascorbic acid gave an equivalent conversion to carboxyl labeled (+)-tartaric acid. These findings clearly show that two distinct processes for the synthesis of (+)-tartaric acid from l-ascorbic acid exist in plants identified as (+)-tartaric acid accumulators. In grape leaves and immature berries, (+)-tartaric acid synthesis proceeds via preservation of a four-carbon fragment derived from carbons 1 through 4 of l-ascorbic acid while carbons 3 through 6 yield (+)-tartaric acid in geranium apices.     

Identification of the persistently bound form of the carcinogen N-acetyl-2-aminofluorene to rat liver DNA in vivo

In this article the structural analysis of the persistently bound form of the carcinogen N-acetyl-2-aminofluorene (AAF) to rat liver DNA in vivo is described. This compound appears to result from the formation of a covalent bond between carbon-3 of the aromatic ring and the amino group of guanine. Experimental evidence from three different approaches has led to the identification of the structure of the persistently DNA-bound AAF moity. First, [3-³H, 9-¹⁴C]N-acetoxy-AAF was reacted with DNA in vitro. As reported previously, a minor product was isolated from enzymatic digests of the reacted DNA, which had chemical and chromatographic properties identical to those of the persistent—AAF moiety in DNA in vivo. The ration ³H/¹⁴C of this product had diminished to the same extent as 3-CH₃S-AAF resulting from the reaction of methionine with [3-³H, 9-¹⁴C]N-acetoxy-AAF.Secondly, reaction of [9-¹⁴C]N-acetoxy-AAF with DNA, which was tritiated in the C-8 positions of the purines, did not result in removal of tritium in the persistent fraction obtained after acid hydrolysis, thus excluding substitution at C-8 and N-7 of guanine. Finally, by reacting N-OSO₃-K-AAF with deoxyguanosine in dimethylsulfoxide-triethylamine, a compound could be isolated, which was identified as 3-(deoxyguanosin-N²-yl)-AAF based on its NMR spectrum and on the mass spectrum of the corresponding guanine derivative obtained after removing deoxyribose by acid hydrolysis. This compound appeared to be identical with the persistently bound form present in DNA hydrolysates from rat liver after injection of [2′-³H]N-hydroxy-AAF.     

Metabolism of nicotine in Nicotiana glauca

A mixture of (?)-nicotine-[2′-³H] and (±)-nicotine-[2′-¹⁴C] was administered to Nicotiana glauca plants for 3 days, resulting in the formation of radioactive nornicotine (49·5% incorporation) and myosmine (2·05% incorporation). Negligible activity was detected in anabasine, cotinine, or 3-acetylpyridine, the last two compounds being added as carriers to the harvested plants. The radioactive nornicotine consisted of 48% (?)-nornicotine-[2′-¹⁴C,³H] and 52% (+)-nornicotine-[2′-¹⁴C]. Thus if (+)-nornicotine is formed from (?)-nicotine the transformation must involve loss of the hydrogen from C-2′. Myosmine is presumably formed from nicotine via nornicotine. However by feeding myosmine-[2′-¹⁴C] to N. glauca it was shown that the dehydrogenation is not reversible, no activity being detected in nornicotine. Nicotinic acid (0·14% incorporation) was a metabolite of myosmine-[2′-¹⁴C]. Essentially all the activity of the nicotinic acid was located on its carboxyl group, indicating that myosmine was a direct precursor.     

Alkaloids and styryllactones from the leaves of Goniothalamus tamirensis

Three new compounds, goniotamirine (1), goniotamiric acid (2), and 3,5-demethoxypiperolide (3) were isolated from the leaves of Goniothalamus tamirensis (Annonaceae), together with sixteen known compounds, (?)-N-nornuciferine (4), (?)-norisocorydine (5), (?)-isocorydine (6), (?)-3-hydroxynornuceferine (7), (?)-O-methylisopiline (8), (?)-anonaine (9), (?)-roemerine (10), (?)-roemeroline (11), (?)-boldine (12), glaunine (13), liriodenine (14), 9-deoxygoniopypyrone (15), 8-epi-9-deoxygoniopypyrone (16), 8-epi-9-deoxygoniopypyrone acetate (17), goniodiol (18) and goniothalamin (19). The structures were established from spectral analysis, including mass spectrometry and 2D-NMR. The absolute configuration of 1 was determined from analysis of its MTPA amide derivatives. The cytotoxicity of all isolates was evaluated against KB cells. Only compound 4 (N-nornuciferine) showed a moderate activity with an IC₅₀ value of 12 μg/mL.     

Highly selective biotransformation of (+)-(1S)- and (−)-(1R)-camphorquinone by Aspergillus wentii

Abstract

To clarify the structures of biotransformation products and metabolic pathways, the biotransformation of monoterpenoids, (+)- and (?)-camphorquinone (1a and b), has been investigated using Aspergillus wentii as a biocatalyst. Compound 1a was converted to (?)-(2S)-exo-hydroxycamphor (2a), (?)-(2S)-endo-hydroxycamphor (3a), (?)-(3S)-exo-hydroxycamphor (4a), (?)-(3S)-endo-hydroxycamphor (5a), and (+)-camphoric acid (6a). Compound 1b was converted to (+)-(2R)-exo-hydroxycamphor (2b), (+)-(2R)-endo-hydroxycamphor (3b), (+)-(3R)-exo-hydroxycamphor (4b), (+)-(3R)-endo-hydroxycamphor (5b), and (?)-camphoric acid (6b). Compound 1a mainly produced 2a (65.0%) with stereoselectivity, whereas 1b afforded 3b (84.3%) with high stereoselectivity. These structures were confirmed by gas chromatography–mass spectrometry, infrared, ¹H nuclear magnetic resonance (NMR), and ¹³C NMR spectral data. The products illustrate the marked ability of A. wentii for enzymatic oxidation and ketone reduction.     

Alkaloids of formosan Fissistigma and Goniothalamus species

Separation of the basic fractions from Formosan Fissistigma glaucescens, F. oldhamii and Goniothalamus amuyon afforded one new quaternary phenanthrene alkaloid, N-methylatherosperminium (15), along with the known alkaloids, (?)-discretamine (1), (?)-tetrahydropalmatine (2), palmatine (3), (?)-asimilobine (4), (?)-norannuradhapurine (5), (?)-crebanine (6), (?)-calycinine (fissoldine, fissistigine A) (7a), (?)-anolobine (8), (?)-xylopine (9), (?)-anonaine (10a), oxocrebanine (11), liriodenine (12), atherosperminine (13), N-noratherosperminine (14) and (+)-O-methylflavinantine (O-methylpallidine) (16).     

Facile synthesis of SSR180575 and discovery of 7-chloro-N,N,5-trimethyl-4-oxo-3(6-[18F]fluoropyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide,a potent pyridazinoindole ligand for PET imaging of TSPO in cancer

A novel synthesis of the translocator protein (TSPO) ligand 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide (SSR180575, 3) was achieved in four steps from commercially available starting materials. Focused structure–activity relationship development about the pyridazinoindole ring at the N3 position led to the discovery of 7-chloro-N,N,5-trimethyl-4-oxo-3(6-fluoropyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide (14), a novel ligand of comparable affinity. Radiolabeling with fluorine-18 (¹⁸F) yielded 7-chloro-N,N,5-trimethyl-4-oxo-3(6-[¹⁸F]fluoropyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide ([¹⁸F]-14) in high radiochemical yield and specific activity. In vivo studies of [¹⁸F]-14 revealed this agent as a promising probe for molecular imaging of glioma.