Chiral dihydroxylation of acronycine: absolute configuration of natural cis-1,2-dihydroxy-1,2-dihydroacronycine and cytotoxicity of (1R,2R)- and (1S,2S)-1,2-diacetoxy-1,2-dihydroacronycine

Sharpless asymmetric dihydroxylation of acronycine (1) gave (1R, 2R)-1,2-dihydroxy-1,2-dihydroacronycine (2) and (1S,2S)-1, 2-dihydroxy-1,2-dihydroacronycine (3), which allowed determination of the absolute configuration of natural cis-1,2-dihydroxy-1, 2-dihydroacronycine as 1R,2R. The cis isomer had been previously isolated from various Sarcomelicope species. Benzylic reduction of isomers 2 and 3 gave the alcohols 4 (2R) and 5 (2S), respectively. Acetylation of 2 and 3 afforded the corresponding esters 6 and 7. No significant difference of cytotoxicity was observed between these (1R,2R)- and (1S,2S)-enantiomers and the recently described, highly active racemic cis-1,2-diacetoxy-1,2-dihydroacronycine, when tested against L-1210 cells in vitro.     

Microbial transformation and butyrylcholinesterase inhibitory activity of (-)-caryophyllene oxide and its derivatives

Microbial transformation of the sesquiterpene (-)-caryophyllene oxide (1) [(1R,4R,5R,9S)-4,5-epoxycaryophyllan-8(13)-ene] by a number of fungi, using a standard two-stage fermentation technique, has afforded as products (1R,4R,5R,9S)-4,5-dihydroxycaryophyllan-8(13)-ene (2), (1S,4R,5R,8S,9S)-clovane-5,9-diol (3), (1R,4R,5R,9S,11R)-4,5-epoxycaryophyllan-8(13)-en-15-ol (4), (1R,4R,5R,9S,11S)-4,5-epoxycaryophyllan-8(13)-en-14-ol (5), (1R,2S,4R,5R,9S)-4,5-epoxy-13-norcaryophyllan-8-one (6), (1R,4R,5R,8S,9S)-4,5-epoxycaryophyllan-13-ol (7), (1R,4R,5R,8S, 9S,13S)-caryolane-5,8,13-triol (8), (1R,3R,4R,5R,8S,9S)-4,5-epoxycaryophyllan-3,13-diol (9), and (1S,4R,5R,8S,9S)-clovane-5,9,12-triol (10). Metabolites 6 and 8-10 were found to be new compounds, as deduced on the basis of spectroscopic techniques. Compounds 1-10 were evaluated for butyrylcholinesterase inhibitory activity, and compound 5 exhibited an IC50 value of 10.9 +/- 0.2 microM.     

Semisynthetic and biotransformation studies of (1S,2E,4S,6R,7E,11E)-2,7,11-cembratriene-4,6-diol

Tobacco-derived (1 S,2 E,4 S,6 R,7 E,11 E)-2,7,11-cembratriene-4,6-diol (1) and (1 S,2 E,4 R,6 R,7 E,11 E)-2,7,11-cembratriene-4,6-diol (2) were first shown to display potential antitumor-promoting activity in the mid-1980s. However, very little is currently understood regarding the structural activity relationships of tobacco cembranoids. The aim of this present study was to explore antiproliferative activity of various derivatives of (1 S,2 E,4 S,6 R,7 E,11 E)-2,7,11-cembratriene-4,6-diol (1) using semisynthetic and biotransformation approaches. Derivatives of 1 include esterified, oxidized, halogenated, and nitrogen- and sulfur-containing compounds (3-17). Biotransformation of 1 using Mucor ramannianus ATCC 9628 and Cunninghamella elegans ATCC 7929 afforded the known 10 S,11 S-epoxy analogue of 1 (4) as the main metabolite. Biotransformation of the 6-O-acetyl analogue (3) using the marine symbiotic Bacillus megaterium strain MO31 afforded (1 S,2 E,4 S,6 R,7 E,11 E,10 R)-2,7,11-cembratriene-4,6,10-triol (18). (1 S,2 E,4 S,6 R,7 E,11 E,13 R)-2,7,11-Cembratriene-4,6,13-triol-6-O-acetate (6), (1 S,2 E,4 S,6 R,7 E,11 E,13 S)-2,7,11-cembratriene-4,6,13-triol-6-O-acetate (7), the rearranged alpha-ketol (1 S,2 E,4 S,7 Z,11 E)-2,7,11-cembratrien-4-ol-6-one (11), and the secocembranoid 12 showed antiproliferative activity against highly malignant +SA mammary epithelial cells with an IC50 range of 15-30 microM.     

Antineoplastic agents 440. Asymmetric synthesis and evaluation of the combretastatin A-1 SAR probes (1S,2S)- and (1R,2R)-1, 2-dihydroxy- 1-(2',3'-dihydroxy-4'-methoxyphenyl)-2-(3' ',4' ',5' '-trimethoxyphenyl)-ethane

The synthetic (E)-isomer (3b) of natural combretastatin A-1 (1a) isolated from the African bushwillow Combretum caffrum was the focus of chiral hydroxylation (Sharpless) reactions as part of a structure-activity relationship study. The resulting (R,R)- and (S,S, )-diols (6 and 7) and synthetic intermediates were evaluated against a series of cancer cell lines, microorganisms, and tubulin. Chiral diols 6 and 7 showed increased activity against the P-388 murine lymphocytic leukemia cell line with ED(50) values of 3.9 and 2.9 microg/mL, respectively, when compared to the precursor (E)-stilbene 3b. In contrast, (E)-stilbene 3b exhibited more potent antibiotic activity than the chiral diols (6 and 7). Both diols, (R,R)-6 and (S, S)-7, displayed less cancer cell growth inhibition and less antibiotic activity than did natural combretastatin A-1 (1a) (P-388 ED(50) 0.25 microg/mL).     

Synthesis of (7S,15S)- and (7R,15S)-dolatrienoic acid

The stereospecific synthesis of (7S,15S)- and (7R,15S)-dolatrienoic acids (2) was achieved using an approach consisting of 16 linear steps. The C-11--C-16 unit was prepared in seven steps from ethyl (S)-lactate and coupled using a trans-selective Wittig--Schlosser reaction to the C-7--C-10 fragment. Chirality at the C-7 position was introduced using an Evan's-type chiral auxiliary in a cobalt-mediated Reformatsky reaction to give the (3S,11S)-aldehyde 24. Subsequent Wittig reaction with a phosphonium salt derived in three steps from tiglic acid gave (7S,15S)-dolatrienoic acid, one of the four possible diastereoisomers of the nonpeptide portion of the strong cancer cell growth inhibitory cyclodepsipeptide dolastatin 14 (1). A second diastereoisomer, (7R,15S)-dolatrienoic acid, was synthesized employing chiral oxazolidinone 21 by an analogous synthetic route.     

Microbial and chemical transformation studies of the bioactive marine sesquiterpenes (S)-(+)-curcuphenol and -curcudiol isolated from a deep reef collection of the Jamaican sponge Didiscus oxeata

Microbial and chemical transformation studies of the marine sesquiterpene phenols (S)-(+)-curcuphenol (1) and (S)-(+)-curcudiol (2), isolated from the Jamaican sponge Didiscus oxeata, were accomplished. Preparative-scale fermentation of 1 with Kluyveromyces marxianus var. lactis (ATCC 2628) has resulted in the isolation of six new metabolites: (S)-(+)-15-hydroxycurcuphenol (3), (S)-(+)-12-hydroxycurcuphenol (4), (S)-(+)-12,15-dihydroxycurcuphenol (5), (S)-(+)-15-hydroxycurcuphenol-12-al (6), (S)-(+)-12-carboxy-10,11-dihydrocurcuphenol (7), and (S)-(+)-12-hydroxy-10,11-dihydrocurcuphenol (8). Fourteen-days incubation of 1 with Aspergillus alliaceus (NRRL 315) afforded the new compounds (S)-(+)-10beta-hydroxycurcudiol (9), (S)-(+)-curcudiol-10-one (10), and (S)-(+)-4-[1-(2-hydroxy-4-methyl)phenyl)]pentanoic acid (11). Rhizopus arrhizus (ATCC 11145) and Rhodotorula glutinus (ATCC 15125) afforded (S)-curcuphenol-1alpha-D-glucopyranoside (12) and (S)-curcudiol-1alpha-D-glucopyranoside (13) when incubated for 6 and 8 days with 1 and 2, respectively. The absolute configuration of C(10) and C(11) of metabolites 7-9 was established by optical rotation computations. Reaction of 1 with NaNO(2) and HCl afforded (S)-(+)-4-nitrocurcuphenol (14) and (S)-(+)-2-nitrocurcuphenol (15) in a 2:1 ratio. Acylation of 1 and 2 with isonicotinoyl chloride afforded the expected esters (S)-(+)-curcuphenol-1-O-isonicotinate (16) and (S)-(+)-curcudiol-1-O-isonicotinate (17), respectively. Curcuphenol (1) shows potent antimicrobial activity against Candida albicans, Cryptococcus neoformans, methicillin-resistant Staphylococcus aureus, and S. aureus with MIC and MFC/MBC ranges of 7.5-25 and 12.5-50 microg/mL, respectively. Compounds 1 and 3 also display in vitro antimalarial activity against Palsmodium falciparium (D6 clone) with MIC values of 3600 and 3800 ng/mL, respectively (selectivity index >1.3). Both compounds were also active against P. falciparium (W2 clone) with MIC values of 1800 (S.I. >2.6) and 2900 (S.I. >1.6) ng/mL, respectively. Compound 14 shows anti-hepatitis B virus activity with an EC(50) of 61 microg/mL.     

Neuroprotective 2-(2-phenylethyl)chromones of Imperata cylindrica

Bioactivity-guided fractionation of the methanolic extract of the rhizomes of Imperata cylindrica afforded a new compound, 5-hydroxy-2-(2-phenylethyl)chromone (1), together with three known compounds, 5-hydroxy-2-[2-(2-hydroxyphenyl)ethyl]chromone (2), flidersiachromone (3), and 5-hydroxy-2-styrylchromone (4). Among these four compounds, 1 and 2 showed significant neuroprotective activity against glutamate-induced neurotoxicity in primary cultures of rat cortical cells.     

Minor sesquiterpenes with new carbon skeletons from the brown alga Dictyopteris divaricata

Five minor sesquiterpenes (1-5) with two novel carbon skeletons, together with a minor new oplopane sesquiterpene (6), have been isolated from the brown alga Dictyopteris divaricata. By means of spectroscopic data including IR, HRMS, 1D and 2D NMR, and CD, their structures including absolute configurations were assigned as (+)-(1R,5S,6S,9R)-3-acetyl-1-hydroxy-6-isopropyl-9-methylbicyclo[4.3.0]non-3-ene (1), (+)-(1R,3S,4S,5R,6S,9R)-3-acetyl-1,4-dihydroxy-6-isopropyl-9-methylbicyclo[4.3.0]nonane (2), (+)-(1R,3R,4R,5R,6S,9R)-3-acetyl-1,4-dihydroxy-6-isopropyl-9-methylbicyclo[4.3.0]nonane (3), (+)-(1S,2R,6S,9R)-1-hydroxy-2-(1-hydroxyethyl)-6-isopropyl-9-methylbicyclo[4.3.0]non-4-en-3-one (4), (-)-(5S,6R,9S)-2-acetyl-5-hydroxy-6-isopropyl-9-methylbicyclo[4.3.0]non-1-en-3-one (5), and (-)-(1S,6S,9R)-4-acetyl-1-hydroxy-6-isopropyl-9-methylbicyclo[4.3.0]non-4-en-3-one (6). Biogenetically, the carbon skeletons of 1-6 may be derived from the co-occurring cadinane skeleton by different ring contraction rearrangements. Compounds 1-6 were inactive (IC(50) > 10 mug/mL) against several human cancer cell lines.     

N-(jasmonoyl)tyrosine-derived compounds from flowers of broad beans (Vicia faba)

Two new amide-linked conjugates of jasmonic acid, N-[(3R,7R)-(-)-jasmonoyl]-(S)-dopa (3) and N-[(3R,7R)-(-)-jasmonoyl]-dopamine (5), were isolated in addition to the known compound N-[(3R,7R)-(-)-jasmonoyl]-(S)-tyrosine (2) from the methanolic extract of flowers of broad bean (Vicia faba). Their structures were proposed on the basis of spectroscopic data (LC-MS/MS) and chromatographic properties on reversed and chiral phases and confirmed by partial syntheses. Furthermore, tyrosine conjugates of two cucurbic acid isomers (7, 8) were detected and characterized by LC-MS. Crude enzyme preparations from flowers of V. faba hydroxylated both (+/-)-2 and N-[(3R,7R/3S,7S)-(-)-jasmonoyl]tyramine [(+/-)-4] to (+/-)-3 and (+/-)-5, respectively, suggesting a possible biosynthetic relationship. In addition, a commercial tyrosinase (mushroom) and a tyrosinase-containing extract from hairy roots of red beet exhibited the same catalytic properties, but with different substrate specificities. The conjugates (+/-)-2, (+/-)-3, (+/-)-4, and (+/-)-5 exhibited in a bioassay low activity to elicit alkaloid formation in comparison to free (+/-)-jasmonic acid [(+/-)-1].     

Jiquilpane hydrocarbon skeleton generated by two successive Wagner-Meerwein rearrangements of longipinane derivatives

The molecular rearrangement of (1R,3S,4S,5S,7S,8R,9S,10R,11R)-7,8,9-triacetyloxylongipinan-1-ol (4) under acidic conditions afforded (1S,4R,5R,7S,8R,9S,10S)-7,8,9-triacetyloxyuruap-3(12)-ene (5), while 6, the C(3)-stereoisomer of 4, after two consecutive Wagner-Meerwein rearrangements followed by two 1,2-hydride migrations, afforded (4R,5R,7S,8S,9S,10S,11S)-7,8,9-triacetyloxyjiquilp-3(12)-ene (7), which possesses a new hydrocarbon skeleton. The structures of the new substances were elucidated by 1D and 2D NMR data in combination with X-ray diffraction analyses of the uruapane, longipinane, and jiquilpane derivatives 5, 6, and 14, respectively. Molecular modeling at the ab initio level was used to study the reaction mechanisms, while deuterium labeling was employed to confirm the C-C bond migrations and the hydride shifts.     

Partial synthesis of (3R,6'R)-alpha-cryptoxanthin and (3R)-beta-cryptoxanthin from (3R,3'R,6'R)-lutein

(3R,3'R,6'R)-Lutein (1), (3R,3'R)-zeaxanthin (2), (3R,6'R)-alpha-cryptoxanthin (3), and (3R)-beta-cryptoxanthin (4) are among dietary hydroxycarotenoids that have been identified in human serum, milk, and ocular tissues. While 1 containing 6% of 2 is commercially available, industrial production of optically active 3 and 4 has not yet been accomplished. Several processes have been developed that transform 1 into 3, 4, and minor quantities of (3R,5'RS,6'R)-3',4'-didehydro-5',6'-dihydro-beta,beta-caroten-3-ol (5) (a regioisomer of 3). In one process, lutein (1) was cleanly deoxygenated to 3 in the presence of trifluoroacetic acid (TFA) and Me3N.BH3 in CH2Cl2 at ambient temperature in nearly 90% yield. Reaction of lutein (1) with a Lewis acid (AlCl3, ZnBr2, ZnI2) and a hydride donor (Me3N.BH3, Na[BH3(OCOCF3)], NaCNBH3) in solvents such as CH2Cl2, THF, and TBME produced similar results. In a two-step process, high-temperature acid-catalyzed dehydration of 1 (propanol/water/acid, 90 degrees C) gave a mixture of anhydroluteins 6, 7, and 8 in 86% yield. In the second step, these dehydration products underwent ionic hydrogenation with TFA/Me3N.BH3 in CH2Cl2 to afford a mixture of 3 and 4 in nearly 80% yield that contained only 1% of 5.     

Biotransformation of (4E,8R)-caryophyll-4(5)-en-8-ol by Botrytis cinerea

Biotransformation of (4E,8R)-caryophyll-4(5)-en-8-ol (1) with Botrytis cinerea afforded 14 products (3-16). Thirteen of these (4-16) are described here for the first time. The main reaction paths involved the isomerization of the double bond at C-4/C-5 and hydroxylation of methyl groups.     

Synthesis of enantiomerically pure (-)-(S)-brevicolline

(-)-(S)-Brevicolline (1) and related beta-carbolines were synthesized using an enantiomerically pure Michael-acceptor synthon (3). Subsequent Pictet-Spengler reaction afforded the tetrahydro-beta-carboline skeleton, which, in turn, was transformed to the beta-carboline by catalytic dehydrogenation.     

Isolations of N-methyl-D-aspartic acid-type glutamate receptor ligands from Micronesian sponges

The bioassay-guided fractionation of the water-soluble extract of the marine sponge Cribrochalina olemda collected in Palau resulted in the isolation of a new amino acid cribronic acid (1): (2S,4R,5R)-5-hydroxy-4-sulfooxypiperidine-2-carboxylic acid. However, aqueous extracts of Stylotella aurantium and Axinella carteri collected in Yap State, Micronesia, afforded a known N-methyl-d-aspartic acid (NMDA)-type glutamate receptor agonist, (2S,4S)-4-sulfooxypiperidine-2-carboxylic acid (2), as a common active principle. Both 1 and 2 induced convulsive behaviors in mice upon intracerebroventricular (icv) injection with ED(50) values of 29 +/- 3.0 and 20 +/- 2.8 pmol/mouse, respectively. Radioligand binding assay using rat cerebrocortical membrane demonstrated that 1 and 2 inhibit the binding of the labeled NMDA receptor ligand [(3)H]CGP39653 at IC(50) values of 83 +/- 15 and 214 +/- 20 nM, respectively. However, 1 and 2 did not displace [(3)H]kainic acid or [(3)H]AMPA. These data indicated that 1 is a selective NMDA-type glutamate receptor ligand with potent convulsant activity in mice.     

Microbial transformation of (-)-guaiol and antibacterial activity of its transformed products

Microbial transformation of the sesquiterpene (-)-guaiol (1) [1(5)-guaien-11-ol] was investigated using three fungi, Rhizopus stolonifer, Cunninghamella elegans, and Macrophomina phaseolina. Fungal transformation of 1 with Rhizopus stolonifer yielded a hydroxylated product, 1-guaiene-9 beta,11-diol (2). In turn, Cunninghamella elegans afforded two mono- and dihydroxylated products, 1-guaiene-3beta,11-diol (3) and 1(5)-guaiene-3beta,9 alpha,11-triol (4), while Macrophomina phaseolina produced two additional oxidative products, 1(5)-guaien-11-ol-6-one (5) and 1-guaien-11-ol-3-one (6). All metabolites were found to be new compounds as deduced on the basis of spectroscopic techniques. Compounds 1-6 were evaluated for their activity against several bacterial strains.     

New dihydrophenanthrene and phenyldihydroisocoumarin constituents of Trema orientalis.

In the course of the chemical investigation of extracts of the trunk bark and root bark of Trema orientalis, three new compounds were isolated, namely, (9S*,10S*)-3-[7-(3,10-dihydroxy-9-hydroxymethyl-2,5-dimethoxy)-9,10-dihydrophenanthrenyl]propenal (1), (9S*,10S*)-3-[7-(5-O-beta-glucopyranosyl-10-hydroxy-9-hydroxymethyl-2,6-dimethoxy)-9,10-dihydrophenanthrenyl]propenal (2), and (3R*,3aR*,4R*,5S*)-6-O-alpha-arabinopyranosyl-8-hydroxy-3-(4-hydroxyphenyl)-4-(4-hydroxyphenyl)-5-(3,5-dihydroxyphenyl)-3,3a-dihydrocyclopenta[1,2,3-de]isobenzopyran-1-one (3, orientoside A). The structures of 1-3 were determined by spectral methods.     

Quirogane,prenopsane, and patzcuarane skeletons obtained by photochemically induced molecular rearrangements of longipinene derivatives

Ultraviolet irradiation of (1R,3S,4S,5S,10R,11R)-1-acetyloxy-7-oxolongipin-8-ene (6), prepared from longipinene diesters isolated from Stevia salicifolia, afforded the new quirogane (7) and prenopsane (8) derivatives, as the major products, together with the minor secondary photoproduct (1R,3R,5R,8S,11S)-1-acetyloxy-7-oxopatzcuar-9-ene (9), which possesses a novel tricyclic sesquiterpene skeleton. The stereostructures of the new compounds 7-9 were mainly determined by NMR techniques including COSY, HSQC, HMBC, and NOESY in combination with molecular modeling obtained by density functional theory calculations. A reaction mechanism accounting for the observed transformations is proposed.     

Nitrogen-containing phorbol esters from Croton ciliatoglandulifer and their effects on cyclooxygenases-1 and -2

Four new phorbol derivatives, 12-O-[(2R)-N,N-dimethyl-3-methylbutanoyl]-4-deoxyphorbol 13-acetate (1), 12-O-[(2S)-N,N-dimethyl-3-methylbutanoyl]-4-deoxyphorbol 13-acetate (2), 12-O-[3-methyl-2-butenoyl]-4-deoxyphorbol 13-acetate (3), and 12-O-[(2R)-N,N-dimethyl-3-methylbutanoyl]phorbol 13-acetate (4), along with six known compounds, were isolated from the aerial parts of Croton ciliatoglandulifer. An anti-inflammatory activity of a hexane extract of this plant was demonstrated against ear edema in mice produced by 12-O-tetradecanoylphorbol 13-acetate, and compounds 1, 4, and 3beta-O-acetyloleanolic acid (5) were active when evaluated against cyclooxygenases-1 and -2.     

New skeletal sesquiterpenoids, caprariolides A-D, from Capraria biflora and their insecticidal activity

Four structurally novel isomeric sesquiterpenes have been isolated from the aerial parts of Capraria biflora. Caprariolides A (1), B (2), C (3), and D (4) have been determined by NMR spectroscopy experiments to be the (3S,5S,9R), (3R,5S,9R), (3R,5R,9R), and (3S,5R, 9R) isomers of 7-(furan-3'-yl)-3,9-dimethyl-1-oxaspiro[4. 5]dec-6-en-2-one, respectively. Both 1 and 2 were found to exhibit insecticidal activity against adult Cylas formicarius elegantulus, one of the most destructive insect pests of the sweet potato, Ipomoea sp.     

Anthelmintic polyfunctional nitrogen-containing terpenoids from marine sponges

The study of the anthelmintic terpenoid components from the Fiji sponge Axinyssa fenestratus (senior synonym of Leucophloeus fenestratus) and two Thailand sponges, Acanthella cavernosa and Topsentia sp., has yielded several new nitrogen-containing sesqui- and diterpenes of known carbon skeletons. Amorphane sesquiterpenes from A. fenestratus included (1R, 6S, 7S, 10S)-10-isothiocyanato-4-amorphene [(+)-1] and new metabolites (1R*, 4S*, 6R*, 7S*)-4-isothiocyanato-9-amorphene [2], 10-isothiocyanato-4,6-amorphadiene [3], and (4S*, 10S*)-10-isothiocyanato-5-amorphen-4-ol [4]. The amorphene (+)-1 of this study may be antipodal to (-)-1 previously isolated from a Hawaiian sponge. A similar relationship may exist at C-1, C-6, C-7 between (+)-2 of this study and (-)-11 isolated from a Palauian sponge. Another known sesquiterpene, axisonitrile 3 [5] was obtained from Topsentia sp. The diterpenes obtained from A. cavernosa included known kalihinols X [6] and Y [8] and new kalihinols J [7] and I [9]. Those terpenoids with potent antiparasite activity include 1, 2, 3-5, and 7-9.