Construction of Acyclic All-Carbon Quaternary Stereocenter Based on Asymmetric Michael Addition of Chiral Amine.

Acyclic asymmetric quaternary stereocenters, which are composed of four carbon-carbon bonds, were finely constructed by utilizing a face-selective alkylation of enolate intermediates derived from an asymmetric Michael addition reaction of a chiral lithium amide with trisubstituted (E)-α,ß-unsaturated esters. The present face-selective alkylation was able to employ diverse alkyl halides as an electrophile to afford various Michael adducts having an all-carbon quaternary stereocenter. With regard to the deprotection of the chiral auxiliary, N-iodosuccinimide used in our previous study did not work in the present cases; however, we found that pyridine iodine monochloride in the presence of H2O was effective to remove the bornyl group and the benzyl group on the amino group to provide the ß-amino ester derivative.

Synthesis and evaluation of (-)- and (+)-[¹¹C]galanthamine as PET tracers for cerebral acetylcholinesterase imaging.

Improved radiopharmaceuticals for imaging cerebral acetylcholinesterase (AChE) are needed for the diagnosis of Alzheimer's disease (AD). Thus, (11)C-labeled (-)-galanthamine and its enantiomers were synthesized as novel agents for imaging the localization and activity of AChE by positron emission tomography (PET). C-11 was incorporated into (-)- and (+)-[(11)C]galanthamine by N-methylation of norgalanthamines with [(11)C]methyl triflate. Simple accumulation of (11)C in the brain was measured in an in vivo biodistribution study using mice, whilst donepezil was used as a blocking agent in analogous in vivo blocking studies. In vitro autoradiography of rat brain tissue was performed to investigate the distribution of (-)-[(11)C]galanthamine, and confirmed the results of PET studies in mice. The radiochemical yields of N-methylation of (-)- and (+)-norgalanthamines were 13.7% and 14.4%, respectively. The highest level of accumulation of (11)C in the brains of mice was observed at 10 min after administration (2.1% ID/g). Intravenous pretreatment with donepezil resulted in a 30% decrease in accumulation of (-)-[(11)C]galanthamine in the striatum; however, levels in the cerebellum were unchanged. In contrast, use of (+)-[(11)C]galanthamine led to accumulation of radioactivity in the striatum equal to that in the cerebellum, and these levels were unaffected by pretreatment with donepezil. In in vitro autoradiography of regional radioactive signals of brain sections showed that pretreatment with either (-)-galanthamine or donepezil blocked the binding of (-)-[(11)C]galanthamine to the striatum, while sagittal PET imaging revealed accumulation of (-)-[(11)C]galanthamine in the brain. These results indicate that (-)-[(11)C]galanthamine showed specific binding to AChE, whereas (+)-[(11)C]-galanthamine accumulated in brain tissue by non-specific binding. Thus, optically pure (-)-[(11)C]galanthamine could be a useful PET tracer for imaging cerebral AChE.

Novel design and synthesis of a radioiodinated glycolipid analog as an acceptor substrate for N-acetylglucosaminyltransferase V.

Guided by the known molecular recognition interactions between N-acetylglucosaminyltransferase V (GnT-V) and certain synthetic substrates, we synthesized a radiolabeled double-stranded glycolipid composed of a long-chain alkyl unit and a radioiodinated phenylalkyl unit, [(125)I]-2-[N-(2-hydroxy-3-hexadecyloxy)propyl-15-(4-iodophenyl)pentadecanecarboxamido]ethyl 2-acetamido-2-deoxy-ß-D-glucopyranosyl-(1→2)-α-D-mannopyranosyl-(1→6)-ß-D-glucopyranoside ([(125)I]2), as a novel intravital glycolipid mimic substrate of GnT-V. The radioactive iodine ((125)I) was incorporated via iododestannylation of the phenyltributyltin derivative, 2-[N-(2-acetoxy-3-hexadecyloxy)propyl-15-(4-tributylstannylphenyl)pentadecanecarboxamido]ethyl 3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-ß-D-glucopyranosyl-(1→2)-3,4,6-O-acetyl-α-D-mannopyranosyl-(1→6)-2,3,4-tri-O-acetyl-ß-D-glucopyranoside (26). Subsequent deacetylation at the final step afforded [(125)I]2.

Novel approach to determining the absolute configurations at the C3-positions of various types of sterols based on an induced circular dichroism.

Circular dichroism (CD) spectra of the 2,2'-binaphthyl ester derived from Δ(5)-sterols showed not bisignate CD but diagnostic CD bands at around 210 and 240 nm. These bands might be attributable to an interaction between an olefinic chromophore and a binaphthyl one. Various types of unsaturated sterols were thus derivatized followed by complete hydrogenation, to give saturated sterols. As a result, CD spectra of the binaphthyl derivatives of the saturated sterols showed bisignate curves centered at 240 nm (3S(ß): positive chirality; 3R(α): negative one). This suggested a straightforward and practical method for discriminating the absolute stereogenic center at the C-3 positions of sterols based on an induced CD. This finding should contribute significantly to the analysis of metabolites of various types of sterols.

Synthesis and evaluation of a radioiodinated trisaccharide derivative as a synthetic substrate for a sensitive N-acetylglucosaminyltransferase V radioassay.

N-acetylglucosaminyltransferase V (GnT-V) is one of the most relevant glycosyltransferases to tumor invasion and metastasis. Based on previous findings of molecular recognition between GnT-V and synthetic substrates, we designed and synthesized a p-iodophenyl-derivatized trisaccharide, 2-(4-iodophenyl)ethyl 6-O-[2-O-(2-acetamido-2-deoxy-ß-D-glucopyranosyl)-α-d-mannopyranosyl]-ß-D-glucopyranoside (IPGMG, 1) and its radiolabeled form, [(125)I]IPGMG ([(125)I]1), for use in assays of GnT-V activity in vitro. The tributyltin derivative, 2-[4-(n-tributylstannyl)phenyl]ethyl 6-O-[2-O-(3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-ß-D-glucopyranosyl)-3,4,6-tri-O-acetyl-α-D-mannopyranosyl]-2,3,4-tri-O-acetyl-ß-D-glucopyranoside (21), was synthesized as a precursor for the preparation of [(125)I]1. The iododestannylation of 21 using hydrogen peroxide as an oxidant followed by deacetylation yielded [(125)I]1. When [(125)I]1 was incubated in GnT-V-expressing cells with a UDP-GlcNAc donor, the production of ß1-6GlcNAc-bearing IPGMG (IPGGMG, 2) was confirmed by radio-HPLC. In kinetic analysis, 1 was found to be a good substrate with a K(m) of 23.7 µM and a V(max) of 159 pmol/h. µg protein. [(125)I]1 would therefore be a useful synthetic substrate for the quantitative determination of GnT-V activity.

Conjugates of 3α-methoxyserrat-14-en-21ß-ol (PJ-1) and 3ß-methoxyserrat-14-en-21ß-ol (PJ-2) as cancer chemopreventive agents.

3α-Methoxyserrat-14-en-21ß-ol (PJ-1) and 3ß-methoxyserrat-14-en-21ß-ol (PJ-2) were conjugated with well-known phenolic compounds, narigenin, hesperetin, genistein, and daidzein (1-8). Other conjugates of PJ-2-3,5-dihydroxy-4-methoxybenzoic acid (9), PJ-2-pyrogallol (10), and derivatives of PJ-1, PJ-2-3,3-dimethyl-succinates (11, 12), PJ-1, PJ-2-succinates (13, 14), PJ-2-glycine (15), PJ-2-piperidine acetic acid (16), and PJ-1 epoxy-3,3-dimethyl-succinate (17) were tested for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). The inhibitory effects of 11 (IC(50) = 251), 12 (IC(50) = 248), and 17 (IC(50) = 230 mol ratio/32 pmol/TPA), were 2-fold stronger than those of the other compounds such as oleanolic acid (IC(50) = 449). Compounds 10, 11, and 17 inhibited mouse skin tumor promotion in an in vivo two-stage carcinogenesis model. The in vivo two-stage mouse-skin carcinogenesis test employed 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter.

One-pot construction of multiple contiguous chiral centers using Michael addition of chiral amine.

Multiple contiguous chiral centers were constructed in one pot using three types of multistep reactions initiated with the Michael addition of N-benzyl-2(R)-methoxy-(+)-10-bornylamide to alpha,beta-unsaturated esters, i.e., asymmetric Michael-aldol reaction, double Michael addition, and double Michael-aldol reaction. The chiral 2-methoxy-10-bornyl group as well as the benzyl group on the amino group of the products in the Michael-aldol reaction could be easily cleaved by treatment with NIS (4 equiv), and beta-amino esters with multiple contiguous chiral centers were obtained in good yield. As an application, the beta-amino-beta'-hydroxy ester obtained in the asymmetric Michael-aldol reaction was converted to the beta-lactam derivative in good yield.

Glycosylation from the non-reducing end using a combination of thioglycoside and glycosyl sulfoxide as the glycosyl donor and the acceptor.

A glycosylation reaction was performed using a combination of thioglycoside and glycosyl sulfoxide, which were prepared with odorless p-octyloxybenzenethiol, as a glycosyl donor and an acceptor, respectively. Promising results were obtained when p-octyloxylphenyl N-phthaloyl-D-thio-glucosaminide was activated with N-iodosuccinimide (NIS) and triflic acid (TfOH) for glycosylation of the hydroxyl group of the C-6 position of derivatives of D-glucosyl sulfoxide. Successive reduction of the resulting disaccharyl sulfoxides provided the corresponding thioglycosides, which could be used as the glycosyl donors in another glycosylation reaction to afford trisaccharides in good yield. The present method would be useful for the block synthesis of glycosyl donors in the total synthesis of blanched oligosaccharides, especially when N-acetylglucosamines are presented at the non-reducing ends.

Hybrids of 3alpha-methoxyserrat-14-en-21beta-ol (PJ-1) and 3beta-methoxyserrat-14-en-21beta-ol (PJ-2) and various anti-oxidants as cancer chemopreventive agents.

3alpha-methoxyserrat-14-en-21beta-ol (1) and 3beta-methoxyserrat-14-en-21beta-ol (2) and their conjugates with curcumin, kojic acid, quercetin, and baicalein (3-18), as well as new analogs (19-24) derived from 1 and 2, were tested for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). The inhibitory effects of 16 (IC50=330 mol ratio/32 pmol/TPA), 9 (IC50=335), 10 (IC50=338), and 15 (IC50=350) were stronger than those of the other compounds and the positive control, oleanolic acid (IC50=449). Compounds 15 and 16, which are conjugates of one molecule each of 1 or 2 and quercetin, inhibited mouse skin tumor promotion in an in vivo two-stage carcinogenesis model. The in vivo two-stage mouse skin carcinogenesis test employed 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter.

Efficient asymmetric synthesis of abeo-abietane-type diterpenoids by using the intramolecular Heck reaction.

The synthesis of the abeo-abietane-type diterpenoids, i.e., (-)-dichroanal B, (-)-dichroanone, and taiwaniaquinone H, was achieved by using the intramolecular asymmetric Heck reaction. Our synthetic routes required fewer steps and gave a much higher overall yield and ee within shorter steps than those for racemic and antipodal forms reported to date (10, 12, and 13 steps with an overall yield of 50%, 40%, and 39%, and 94%, 98%, and 98% ee, respectively).

Straightforward approach to the discrimination of (4R)- and (4S)-beta-isocryptoxanthin from a conformationally insensitive CD band.

A straightforward strategy is reported for chiral discrimination in a specified carotenoid using a CD band, which is insensitive to conformational changes, computed by quantum chemical calculation.

Isolation and identification of a novel aromatic amine mutagen produced by the Maillard reaction.

To clarify the formation of mutagens in the Maillard reaction of glucose and amino acids, 20 amino acids were separately incubated with glucose in the presence or absence of hydroxyl radicals produced by the Fenton reaction. After 1 week at 37 degrees C and pH 7.4, the reaction mixtures of glucose and tryptophan with and without the Fenton reagent showed mutagenicity toward Salmonella typhimurium YG1024 in the presence of a mammalian metabolic system (S9 mix). To identify mutagens in the reaction mixture, blue rayon-adsorbed material from a mixture of glucose, tryptophan, and the Fenton reagent was separated by column chromatography using various solid and mobile phases, and one mutagen, which accounted for 18% of the total mutagenicity of the reaction mixture, was isolated. The chemical structure of the mutagen was determined to be 5-amino-6-hydroxy-8H-benzo[6,7]azepino[5,4,3-de]quinolin-7-one (ABAQ) on the basis of ESI mass, high-resolution APCI mass, (1)H NMR, (13)C NMR, and IR spectral analyses and chemical synthesis of the mutagen. The novel aromatic amine showed high mutagenicity toward S. typhimurium TA98 and YG1024 with S9 mix, inducing 857 revertants of TA98 and 6007 revertants of YG1024/microg, respectively. The mutagenicity of ABAQ was comparable to that of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, which is a mutagenic and carcinogenic hetrocyclic amine in cooked meat and fish formed through the Maillard reaction at high temperature.

Novel 3alpha-methoxyserrat-14-en-21beta-ol (PJ-1) and 3beta-methoxyserrat-14-en-21beta-ol (PJ-2)-curcumin, kojic acid, quercetin, and baicalein conjugates as HIV agents.

Sixteen novel compounds; 3alpha-methoxyserrat-14-en-21beta-ol (1) and 3beta-methoxyserrat-14-en-21beta-ol (2) and their curcumin, kojic acid, quercetin, and baicalein conjugates (3)-(18) were designed, synthesized, and evaluated for in vitro anti-HIV-1 reverse transcriptase (RT) activity in infected C8166-CCR5 cells, a human CD4(+) T-lymphocyte cell line. Among them, kojic acid derivatives, 9-12 showed significant biological activity. In particular, the compound 13, the conjugate of two molecules of 3alpha-methoxyserrat-14-en-21beta-ol (1) and one molecule of kojic acid, exerted significant anti-HIV activity with an EC50 value of 0.12microg/mL.

Inhibitors against glycosidases as medicines.

Glycosidases mediate the digestion of oligosaccharides in the small intestine as well as the processing of cell surface oligosaccharides, which play important roles in cell to cell recognition during infections, metastasis, and immune responses. Thus, agents that control the activities of glycosidases could have therapeutic effects against many carbohydrate-related diseases. In fact, many fruitful efforts have been made to design and synthesize glycosidase inhibitors as clinically practical medicines. This review summarizes the current stage of development of such inhibitors to treat diabetes, influenza, virus infection of HIV, tumor metastasis, and glycosyl sphingo lipid (GSL) storage diseases.

Asymmetric Michael addition of a recyclable chiral amine: inversion of stereoselectivity caused by the difference of ethereal solvents.

The Michael addition of a chiral amine [(-)- 6] to alpha,beta-unsaturated esters ( 4) was attained and the stereoselectivity was inverted by changing the solvent from diethyl ether to tetrahydrofuran when alpha,beta-unsaturated esters having an aromatic ring at the beta-position were employed. In addition, the chiral auxiliary in the Michael adducts ( 9A) was facilely removed with N-iodosuccinimide to afford beta-amino esters ( 10A) and 2-methoxy- d-bornylaldehyde ( 11), which can be reclaimed to the chiral amine ( 6) by reductive amination.

Efficient total synthesis of (+)-negamycin, a potential chemotherapeutic agent for genetic diseases.

Herein, we describe an efficient strategy for the total synthesis of (+)-negamycin using commercially available achiral N-Boc-2-aminoacetaldehyde as starting material with 42% overall yield for a limited number of steps.

A novel transforming growth factor beta receptor kinase inhibitor, A-77, prevents the peritoneal dissemination of scirrhous gastric carcinoma.

PURPOSE: Transforming growth factor beta receptor (TGFbeta-R) is reported to correlate with the malignant potential of scirrhous gastric carcinoma. The aim of the current study is to clarify the possibility of molecular target therapy with a TGFbeta-R inhibitor, A-77, for the treatment of peritoneal dissemination of scirrhous gastric cancer. EXPERIMENTAL DESIGN: Three scirrhous gastric cancer cell lines and two fibroblasts were used. For in vivo experiments, the A-77 was administered i.p. to mouse models of peritoneal dissemination. The influences of A-77 on the adhesion ability, invasion ability, and the expression of adhesion molecules were examined in vitro. RESULTS: The A-77 administration resulted in a significantly (P < 0.01) better prognosis for the mice with peritoneal dissemination (median survival time, 51 days), compared with the control (median survival time, 25 days). A-77 therefore significantly (P < 0.01) decreased the weight and number of metastatic nodes. The adhesive ability and invasion ability of cancer cells were significantly decreased by A-77. A-77 decreased the expression of alpha(2), alpha(3), and alpha(5) integrins in gastric cancer cells. The histologic findings showed the degree of fibrosis to be less in the tumors treated by A-77. A-77 decreased the growth of fibroblast and invasion-stimulating activity of fibroblasts on cancer cells. CONCLUSION: The TGFbeta-R inhibitor, A-77, decreased the expression of integrins in cancer cells and the proliferation of fibroblasts, which resulted in the decreased adhesive and invasive abilities of scirrhous gastric cancer cells to peritoneum. A-77 is thus considered to be useful for the inhibition of peritoneal dissemination of scirrhous gastric carcinoma.

Oral administration of (11E)-13-oxo-15,16-dinorlabda-8(20),11-dien-19-oic acid strongly reduces photocarcinogenesis in mouse skin exposed to UV-B irradiation.

(11E)-13-Oxo-15,16-dinorlabda-8(20),11-dien-19-oic Acid (1), obtained either from the stem bark of Thuja standishii or readily prepared in larger quantities from the related constituent 2, was found to significantly reduce the formation of papilloma in an in vivo two-stage mouse-skin-carcinogenesis model. Carcinogenesis was initiated by skin exposure to UV-B irradiation and promoted by topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA). Oral administration of 1, starting one week before and ending one week after irradiation, exhibited remarkable effects. First, papilloma formation started two weeks later than in the control group (lacking 1). Second, the average number of skin papilloma after 20 weeks was reduced by ca. 50% in the test group relative to the control.

Synthesis of DL-standishinal and its related compounds for the studies on structure-activity relationship of inhibitory activity against aromatase.

DL-Standishinal (1), an aromatase inhibitor isolated from Thuja standishii, was synthesized in 15 steps from p-formylanisole via aldol reaction of 12-hydroxy-6,7-secoabieta-8,11,13-trien-6,7-dial (2). In the present study, we found that the aldol condensation of 2 proceeded in excellent yield with the protonic catalyst such as d-camphorsulfonic acid in CH(2)Cl(2). Moreover, structure-activity relationship of 1 and its related compounds was studied and it was revealed that the isomers having cis-configuration on the A/B-ring generally exhibited more potent inhibitory activities against aromatase than those with trans-configuration.