Stereoconvergent approach for synthesizing enantiopure 5, 6-dialkylpipecolic acids

Investigating a general route for synthesizing pipecolic acid ) piperidine-2-carboxylic acid ( derivatives with substituents at the 3-, 4-, 5- and 6-position, we discovered a stereoconvergent process that provides an effective means for making 5, 6-dialkyl-epsilonpipecolate (Scheme 1, PhF = 9-phenylfluoren-9-yl). Hydrogenation of diastereomeric mixtures of gamma-oxo gamma-hydroxy and gamma-acetoxy alpha-N-(PhF)amino tert-butyl esters causes the eventual loss of the gamma-substituent to furnish an azadiene intermediate that can reduce diastereoselectively to 5, 6-dialkylpipecolate having the all cis relative stereoconfiguration. Five enantiopure (>94% ee) 5,6-dialkylpipecolic acids were synthesized, employing aspartic acid as an inexpensive chiral educt in this process.     

Synthesis of (R)- and (S)- muscone

(R)-(-)-Muscone (3-methylcyclopentadecanone, 1) the key perfumery component isolated from the male musk deer, Moschus moschiferus,* was synthesized from the easily available chiral building block, (R)-3-tert-butoxycarbonyl-2-methylpropanoic acid (2), by employing ring-closing olefin metathesis (RCM). Antipode (+)-1 was also synthesized in a similar manner from tert-butyl (S)-3-methoxycarbonylbutanoate (10). *(a) Walbaum, H. J. J. Prakt. Chem., 73, 488 (1906); (b) Ruzicka, L., Further considerations on the constitution of muscone. Helv. Chim. Acta, 9, 715, 1008-1017 (1926).     

Synthesis of the mitogenic S-[2,3-bis(palmitoyloxy)propyl]-N-palmitoylpentapeptide from Escherichia coli lipoprotein

The N-terminal pentapeptide of the lipoprotein from the outer membrane of Escherichia coli was obtained by coupling S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-N-palmitoyl-(R)-cysteine to O-tert-butylseryl-O-tert-butyl-seryl-asparaginyl-alanine tert-butyl ester followed by deprotection with trifluoroacetic acid. The tetrapeptide was built up from alanine tert-butyl ester with N-9-fluorenylmethyloxycarbonyl protected amino acids. S-[2,3-Bis(palmitoyloxy)propyl]-N-palmitoylcysteine was obtained from N,N'-dipalmitoylcystine di-tert-butyl ester via reduction to the thiol, and S-alkylation with racemic 3-bromo-1,2-propanediol followed by esterification with palmitic acid in the presence of dicyclohexylcarbodiimide/dimethylaminopyridine and deprotection with trifluoroacetic acid. The compounds were characterized unequivocally by 13C-NMR and mass spectra. The diastereomers of S-[2,3-bis(palmitoyloxy)propyl]-N-palmitoylcysteine tert-butyl ester with opposite configuration at the propyl-C-2 atom could be separated on a silica-gel column.     

Synthesis,antioxidative and antiviral activity of hydroxycinnamic acid amides of thiazole containing amino acid

The synthesis and the biological (antioxidant and antiviral) activities of novel hydroxycinnamic acid amides of a thiazole containing TFA.valine-4-carboxylic acid ethyl ester are reported. The amides have been synthesized from p-coumaric, ferulic and sinapic acids with the corresponding TFA.valine-thiazole-4-carboxylic acid ethyl ester using the coupling reagent N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and 4-(dimethylamino) pyridine (DMAP) as a catalyst. The antioxidant properties of the newly synthesized amides have been studied for then antioxidative activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH)* test. The newly synthesized compounds have been tested against the replication in vitro of influenza virus A (H3N2) and human herpes virus 1 and 2 (HSV-1 and HSV-2).     

Synthesis and biological evaluation of 3-substituted-benzofuran-2-carboxylic esters as a novel class of ischemic cell death inhibitors

A series of 3-substituted-benzofuran-2-carboxylic esters was synthesized and evaluated for biological activity as ischemic cell death inhibitors in H9c2 cells and rat primary cardiac myocytes under conditions of oxygen and glucose deprivation. The introduction of a sulfur atom at the three-position substituent of the benzofuran ring markedly improved ischemic cell death inhibitory potency. In particular, 3-[2-(4-nitro-phenylsulfanyl)-acetylamino]-benzofuran-2-carboxylic acid ester (10) (EC(50)=0.532 μM, cell death=6.18%) and 4-chloro-3-[3-(pyridin-2-ylsulfanyl)-propionylamino]-benzofuran-2-carboxylic ester (18) (EC(50)=0.557 μM, cell death=7.02%) were shown to be the most potent in this series of benzofuran analogs.     

4-Hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester derivatives as potent anti-tumor agents

Based on the structure of 4-hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester (1), which exhibits selective cytotoxicity against a tumorigenic cell line, (2,4-dimethoxyphenyl)-(4-hydroxy-3-methyl-6-phenylbenzofuran-2-yl)-methanone (18m) was designed and synthesized as a biologically stable derivative containing no ester group. Although the potency of 18m was almost the same as our initial hit compound 1, 18m is expected to last longer in the human body as an anticancer agent.     

Indole alkaloids from a culture of the fungus Aporpium caryae

In a screening for antifungal metabolites, two indole compounds of mixed biogenesis, 1H-indole-3-carboxylic acid, 1-(1,1-dimethyl-2-propenyl) methyl ester and 1H-indole-3-carboxylic acid, 1-(2,3-dihydroxy-1,1-dimethylpropyl) methyl ester were isolated from a culture of the basidiomycete Aporpiums caryae. The structural elucidation of these compounds was accomplished by spectroscopic methods.     

Synthesis and thrombolytic activity of pseudopeptides related to fibrinogen fragment

Two kinds of linkers consisting of 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, ARPAK, GRPAK and QRPAK were synthesized. The thrombolytic activities in vivo indicated that the coupling position of 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in the peptides effected on the potencies significantly. When the C-terminal of the peptides was amidated by 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, the thrombolytic potency of the peptides was enhanced or kept. When the N-terminal of the peptides was acylated by 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, however, the thrombolytic effect of the peptides was banished. The expected specific beta II'-turn conformation and the stability to trypsin in the pseudopeptides with 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in its C-terminal may be responsible for the enhanced thrombolytic potency.     

Synthesis of 3-(3-pyridyl)- and 3-(3-benzo[b]thienyl)-D-alanine

The DL-arylamino acid ethyl ester derivatives of beta-(3-pyridyl)-DL-alanine, and beta-(3-benzo[b]thienyl)-DL-alanine were synthesized by diethyl acetamidomalonate condensation with the respective arylmethyl halides followed by partial hydrolysis to the monoethyl ester and decarboxylation. Each derivative was enzymatically resolved to a separable mixture of the corresponding N-acetyl-L-amino acid and the unchanged D amino acid derivative. Acidic hydrolysis of the latter gave the corresponding D-amino acid, the optical purity of which was established by HPLC analysis of the 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate (GITC) derivative. The free D amino acids were converted to D-BOC derivatives by reaction with di-tert-butyldicarbonate in tert-butyl alcohol, water and sodium hydroxide.     

Novel 3-dodecanoylindole-2-carboxylic acid inhibitors of cytosolic phospholipase A(2)

Derivatives of 1-[2-(4-carboxyphenoxy)ethyl]-3-dodecanoylindole-2-carboxylic acid (4) with modified substituents at the indole-1-position were synthesized and evaluated for their ability to inhibit the arachidonic acid release in human platelets mediated by the cytosolic phospholipase A(2). One of the most active compounds obtained was 26 with an IC(50) of 0.44 microM.     

A library synthesis of 4-hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester derivatives as anti-tumor agents

As a result of a hit-to-lead program using a technique of solution-phase parallel synthesis, a highly potent (2,4-dimethoxyphenyl)-[6-(3-fluorophenyl)-4-hydroxy-3-methylbenzofuran-2-yl]methanone (15b) was synthesized as an optimized derivative of 4-hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester (1), which was discovered as a screening hit from small-molecule libraries and exhibited selective cytotoxicity against a tumorigenic cell line.     

In vitro and in vivo assessment of the antioxidant activity of melatonin and related indole derivatives

Effects of melatonin and some structurally related indole compounds were studied by in vitro methods such as (i) an inhibition of the hyaluronic acid degradation and (ii) a standard lipid peroxidation assay. In vivo approach was based on the alloxan model of hyperglycaemia. Reduction of the viscosity of a hyaluronic acid solution in the reaction mixture was inhibited by tryptamine (91% inhibition), as well as by indole-3-carboxylic acid and indomethacin (80% and 77% inhibition, respectively). Lipid peroxidation with tert-butyl hydroperoxide as a source of radicals was followed by the formation of thiobarbituric acid reactive substances. Tested drugs inhibited lipid peroxidation in the order: tryptamine (59%) > indole-2-carboxylic acid (38%) > indomethacin (26%) > melatonin and indole-3-carboxylic acid (13%). In vivo, alloxan-induced hyperglycaemia was reduced in mice pretreated with drugs tested. The highest protective effect was observed with indomethacin (52% inhibition), followed by tryptamine and melatonin (18% and 16% inhibition, respectively).     

Synthesis of affinity ligands and radioactive probes for isolation and study of myo-inositol 1,4,5-trisphosphate binding proteins

To synthesize an affinity matrix for isolation of D-myo-inositol 1,4,5-trisphosphate binding proteins, racemic 3-cyclohexene-1-carboxaldehyde was oxidized and converted to a mixture of trans-3,4-di-hydroxycyclohexane-1-carboxylic acid methyl ester isomers, which was phosphorylated and separated into (+-)-(1R,3R,4R)- and (+-)-(1R,3S,4S)-trans-3,4-bis[(diphenoxyphosphoryl)oxy]cyclohex an e-1- carboxylic acid methyl esters. Each of these racemic compounds was hydrogenolyzed and reacted with ethylenediamine to give a monoamide, N-(2-aminoethyl)-bis(phosphonyloxy)cyclohexane-1-carboxamide, that was coupled to cyanogen bromide activated Sepharose 4B to provide the desired affinity matrices. The intermediate trans-3,4-bis[(diphenoxyphosphoryl)oxy]cyclohexane-1-carboxylic acid methyl ester was also reduced with lithium borotritide to give the (hydroxy[3H]methyl)cyclohexane derivative, which was phosphorylated and hydrogenolyzed to yield trans-3,4-bis(phosphonyloxy)-1-[(phosphonyloxy)[3H]methyl]cy clohexane, a radiolabeled analogue of inositol 1,4,5-trisphosphate. The carboxamide was also coupled to 4-azidosalicylic acid, and the product was iodinated to provide a 125I-radiolabeled photoactivatable cross-linking derivative of cyclohexanediol bisphosphate.     

Biocatalytic ammonolysis of (5S)-4,5-dihydro-1H-pyrrole-1,5-dicarboxylic acid, 1-(1,1-dimethylethyl)-5-ethyl ester: preparation of an intermediate to the dipeptidyl peptidase IV inhibitor Saxagliptin

An efficient biocatalytic method has been developed for the conversion of (5S)-4,5-dihydro-1H-pyrrole-1,5-dicarboxylic acid, 1-(1,1-dimethylethyl)-5-ethyl ester (1) into the corresponding amide (5S)-5-aminocarbonyl-4,5-dihydro-1H-pyrrole-1-carboxylic acid, 1-(1,1-dimethylethyl)ester (2), which is a critical intermediate in the synthesis of the dipeptidyl peptidase IV (DPP4) inhibitor Saxagliptin (3). Candida antartica lipase B mediates ammonolysis of the ester with ammonium carbamate as ammonia donor to yield up to 71% of the amide. The inclusion of Ascarite and calcium chloride as adsorbents for carbon dioxide and ethanol byproducts, respectively, increases the yield to 98%, thereby offering an efficient and practical alternative to chemical routes which yield 57-64%.     

Synthesis of radiolabeled biphenylsulfonamide matrix metalloproteinase inhibitors as new potential PET cancer imaging agents

Novel matrix metalloproteinase (MMP) inhibitor radiotracers, (S)-3-methyl-2-(2',3',4'-methoxybiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1a-c), (S)-3-methyl-2-(2',3',4'-fluorobiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1d-f), and (S)-3-methyl-2-(4'-nitrobiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1g), a series of substituted biphenylsulfonamide derivatives, have been synthesized for evaluation as new potential positron emission tomography (PET) cancer imaging agents.     

Substituted furans as potent lipoxygenase inhibitors: Synthesis,in vitro and molecular docking studies

A number of 2-methyl-4-(2-oxo-2-phenyl-ethyl)-5-phenyl-furan-3-carboxylic acid alkyl ester derivatives (3a–j) were synthesized and evaluated for their in vitro inhibitory activity on soybean lipoxygenase enzyme. Among the screened compounds, 5-(4-bromo-phenyl)-4-[2-(4-bromo-phenyl)-2-oxo-ethyl]-2-methyl-furan-3-carboxylic acid methyl ester (3g) has been found to exhibit potent inhibitory activity with IC₅₀12.8 μM using nordihydroguaiaretic acid (NDGA) as standard. Molecular modeling was employed for better understanding of the binding between compounds and soybean lipoxygenase enzyme. The predicted binding energy values correlated well with the observed in vitro data.     

棕色扁海绵中的吡咯生物碱

从中国南海棕色扁海绵Phakellia fusca Schimidt的乙醇浸提物中,分离得到3个吡咯生物碱,结合理化性质,波谱分析,文献检索,确定其结构分别为4,5-二溴-1H-吡咯-2-甲酸甲酯(1)、4,5-二溴-3-氰-1H-吡咯-2-甲酸甲酯(2)、4,5-二溴-1H-吡咯-2-甲酰氨(3)。其中化合物(2)未见文献报道。     

An efficient access to protected disialylated glycohexaosyl threonine present on the leukosialin of activated T-lymphocytes

The total synthesis of the threonine-linked core 2 class disialylated hexasaccharide in a completely protected form was accomplished for the first time. The L-threonine conjugate, N-(9-fluorenylmethoxycarbonyl)-O-[(5-acetamido-4,7,8,9-tetra-O-ben zyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid)-(2-->3)-(2,6-di-O-benzyl-beta-D-galactopyranosyl)-(1-->4)-2-acetam ido-2-deoxy-3,6-di-O-benzyl-beta-D-glucopyranosyl-(1-->6)-[(5-acetamido- 4,7,8,9-tetra-O-benzyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulo pyranosylonic acid)-(2-->3)-2,6-di-O-benzyl-beta-D-galactopyranosyl-(1-->3)]-2-acetami do-2-deoxy-alpha-D-galactopyranosyl-(1d-->4c:1f-->4e)-dilactone ]-L-threonine allyl ester was synthesized via stereocontrolled glycosylations employing readily accessible monosaccharidic blocks; t-butyl-diphenylsilyl-2-azido-2-deoxy-3,6-di-O-benzyl-beta-D-gluco pyranose, N-(9-fluorenylmethoxycarbonyl)-O-(2-azido-6-O-t-butyldimethylsilyl -2-deoxy-alpha-D-galactopyranosyl)-L-threonine allyl ester, 8, 9 and N-(9-fluorenylmethoxycarbonyl)-O-(2-azido-4,6-O-benzylidene-3-O-ch loroacetyl-2-deoxy-alpha-D-galactopyranosyl)-L-threonine allyl ester. For the introduction of the amino acid, the azide group was used to temporarily mask the amino group of GalNAc so as to obtain an alpha-glycosidic linkage without participation from the C-2 substituent. The threonine was attached to the sugar unit at the monosaccharide stage to avoid loss of oligosaccharide at a later stage. The Fmoc and allyl ester protected amino acid at the reducing end facilitates efficient glycopeptide synthesis on solid-phase support.     

Stereoselective synthesis of 2,3,7-trimethylcyclooctanone and related compounds and determination of their relative and absolute configurations by the MalphaNP acid method

The copper/chiral phosphoramidite (L(1))-catalyzed conjugate addition of dimethylzinc to cycloocta-2,7-dienone 4, followed by the methylation of the intermediate enolate, yielded a single isomer of 7,8-dimethylcyclooct-2-enone (+)-5. Compound (+)-5 was subjected to the second conjugate addition with ent-L(1) giving only one stereoisomer of 2,3,7-trimethylcyclooctanone (+)-6, which was converted to 2,3,7-trimethylcyclooctanol 7. To determine the relative and absolute configurations of these compounds, the (1)H NMR anisotropy method using (S)-(+)-2-methoxy-2-(1-naphthyl)propionic acid {(S)-(+)-MalphaNP acid} 1 was applied. Racemic alcohol (+/-)-7 was esterified with (S)-(+)-MalphaNP acid 1 yielding diastereomeric esters, which were efficiently separated by HPLC on silica gel affording the first-eluted MalphaNP ester (-)-10a and the second-eluted one (-)-10b. The relative and absolute configurations of ester (-)-10a were determined to be (S;1R,2S,3R,7S) by analyzing the (1)H and (13)C NMR spectra of (-)-10a and (-)-10b, especially their HSQC-TOCSY and NOESY spectra, and by applying the MalphaNP anisotropy method. The alcohol 7 formed from (+)-6 was similarly esterified with (S)-(+)-MalphaNP acid 1 yielding an MalphaNP ester, which was identical with (-)-10a, and the relative and absolute configurations of 2,3,7-trimethylcyclooctanone (+)-6 were determined to be (2S,3R,7S).