Synthesis and antiproliferative activity in vitro of new derivatives of 3-aminopyrazolo[3,4-b]pyridine. Part 1. Reaction of 3-aminopyrazolo[3,4-b]pyridine with 1,3-, 1,4-diketones and alpha,beta-unsaturated ketones

The synthesis of several new pyrazolo[3,4-b]pyridine, pyrido[2',3':3,4]-pyrazolo[1,5-a]pyrimidine and imidazo[1',2':1,5]pyrazolo[3,4-b]pyridine derivatives is described. The obtained compounds were tested for their antiproliferative activity in vitro. One of them, 4-phenyl-2-(3,4,5-trimethoxy-beta-styrylo)pyrido- [2',3':3,4]pyrazolo[1,5-a]pyrimidine (9), revealed cytotoxic properties against the cells of all three human cancer cell lines applied. Another one, 2,4-dimethyl-pyrido[2',3':3,4]pyrazolo[1,5-a]-pyrimidine (2), revealed weak cytotoxic activity only against the cells of human bladder cancer cell line HCV29T. All other compounds tested did not reveal any cytotoxic activity.     

Synthesis of 11H-pyridocarbazoles and derivatives. Comparison of their DNA binding and antitumor activity with those of 6H- and 7H-pyridocarbazoles

The 8-methoxy- and 8-hydroxy-11H-pyrido[2,3-a]-, -[3,4-a]-, -[4,3-a]-, and [3,2-a]carbazoles were synthesized as potential DNA intercalating antitumor drugs. The structure of these compounds was confirmed by 1H NMR study including NOE experiments. The DNA binding properties of substituted and unsubstituted (8-H) heterocycles were determined by using their hydrochlorides or methiodides. These derivatives are able to bind to DNA with an affinity varying from 2.0 X 10(4) to 1.0 X 10(6) M-1, but most of them are unable to intercalate in contrast with the behavior of 6H- and 7H-pyridocarbazole analogues. The cytotoxicity of 11H-pyridocarbazoles, measured on L1210 cells in vitro, is much lower than those of 6H- and 7H-pyridocarbazole analogues.     

Synthesis and antitumor activity of cyclophosphamide analogs. 1. Benzo annulated cyclophosphamide and related systems.

Synthesis of 2-[bis(2-chloroethyl)amino]-3,4-dihydro-2H-1,3,2-benzoxazaphosphorin 2-oxide (2), which is a benzo annulated analog of cyclophosphamide [2-bis(2-chloroethyl)aminotetrahydro-2H-1,3,2-oxazaphosphorin 2-oxide (1)], was carried out in order to test for possible increased antitumor activity relative to 1 due to the presence of an oxidatively reactive C-4 benzylic site in 2. A structural isomer of 2, 2-[bis(2-chloroethyl)amino]-1,4-dihydro-2H-3,1,2-benzoxazaphosphorin 2-oxide (3), and cognate systems 2-[bis(2-chloroethyl)amino]-1,2,3,4-tetrahydro-1,3,2-benzodiazaphosphorin 2-oxide (4) and 2-[bis(2-chloroethyl)amino]-4H-1,3,2-benzodioxaphosphorin 2-oxide (5) were also prepared for comparative purposes. In vivo antitumor evaluation in mice against L1210 lymphoid leukemia indicated no significant activity for compound 2. Compounds 3 and 4 were likewise found to be inactive and only marginal activity was exhibited by 5.     

Impurity profile study of zaleplon

Zaleplon is a pyrazolopyrimidine derivative and possesses sedative and hypnotic properties. Seven unknown impurities in zaleplon bulk drug at levels below 0.1% were detected by reverse-phase high performance liquid chromatography (HPLC). The starting material, 3-amino-4-cyanopyrazole and an intermediate, N-[3-[3-(dimethylamino)-1-oxo-2-propenyl]-phenyl]-N-ethylacetamide (DOPEA) were also present in the sample at a level below 0.1%. The molecular weights of impurities were determined by LC-MS analysis. These impurities were isolated from crude samples of zaleplon using reverse-phase preparative HPLC. Based on the spectral data the structures of these impurities were characterized as, N-(3-(3-(4-amino-2H-pyrazolo [3,4-d]pyrimidin-6-yl) pyrazolo[1,5-a] pyrimidin-7-yl)phenyl)-N-ethylacetamide (impurity I); N-[3-(3-carboxamidopyrazolo[1,5-a]pyrimidin-7-yl)phenyl]-N-ethylacetamide (impurity II); N-[3-(3-cyanopyrazolo[1,5-a]pyrimidin-7-yl)phenyl]acetamide (impurity III); N-[3-(3-cyanopyrazolo [1,5-a]pyrimidin-7-yl)phenyl]-N-methylacetamide (impurity IV); N-[3-(3-cyanopyrazolo[1,5-a] pyrimidin-5-yl)phenyl]-N-ethylacetamide (impurity V); N-[3-(3-cyanopyrazolo[1,5-a] pyrimidin-7-yl)phenyl]-N-ethylamine (impurity VI); N-[3-(3-cyano-6-[(E)-3-((N-ethyl-N-acetyl)amino)phenyl-3-oxoprop-1-enyl] pyrazolo[1,5-a]pyrimidin-7-yl) phenyl]-N-ethylacetamide (impurity VII). Structural elucidation of all impurities by spectral data ((1)H NMR, (13)C NMR, MS and IR) and formation of these impurities are discussed in detail.     

Benzimidazole condensed ring systems: New synthesis and antineoplastic activity of substituted 3,4-dihydro- and 1,2,3,4-tetrahydro-benzo [4,5]imidazo[1,2-a]pyrinnidine derivatives

As part of an ongoing effort to develop new antineoplastic agents, a series of substituted 3,4-dihydro- and 1,2,3,4-tetrahydro-benzo[4,5]imidazo[1,2-a]pyrimidine derivatives (5-19) were synthesized. 1,2,3,4-Tetrahydrobenzo[4,5]imidazo[1,2-a]pyrimidine-2-one derivatives (5-7) were prepared via one-pot two-component thermal cyclization reaction of 2-aminobenzimidazole 1 and P-substituted methyl cinnamates (2-4). Vilsmir-Haack formylation of these derivatives (5-7) afforded the 2-chloro-3-carboxaldehyde targets (8-10) followed by nucleophilic displacement of the chloro atom in the 3-carboxaldehyde compounds (8-10) to yield the remaining final targets (11-19). The structures of the synthesized derivatives (5-19) were confirmed by means of IR, 1H NMR, MS and elemental analyses. The synthesized derivatives (5-19) were subjected to the National Cancer Institute (NCI) in vitro disease human cell screening panel assay. 2-Chloro-4-phenyl-3,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carboxyaldehyde (8, NCI 722731) and 4-(4-methoxyphenyl)-2-(4-methylpiperazin-1-yl)-3,4-dihydrobenzo[4,5]imidazo [1,2-a]pyrimidine-3-carboxaldehyde (18, NCI 722739) showed a variable degree of antineoplastic activity against some of the cell lines tested. 2-Chloro-4-(4-nitrophenyl)-3,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carboxyaldehyde (10, NCI 722743) exhibited good in vitro antineoplastic activity with subpanel disease selectivity against all the cell lines tested with log10 G150 (M), the concentration that inhibits 50% of cell growth, values ranging from -5.08 to < -8.00.     

Synthesis and biological evaluation of new thiazolopyrimidines

In this study, a series of 4-amino-5-cyano-3-substituted-2,3-dihydrothiazol-2-thiones (1a-c), as well as their triazolo and triazinopyrimidine derivatives such as 8-substituted-3-benzyl-5-methylthiazolo[5,4-e][1,2,4] triazolo[1,5-c]pyrimidin-2-thiones (4-6, 10) and 3-benzyl-5-methyl thiazolo[5,4-e]pyrimidino[3,4-b][1,2,4]triazin-2-thiones (7a-b) were prepared as potential antimicrobial and antitumor agents. Some of the tested compounds showed promising antimicrobial activity and non of them showed any appreciable antitumor activity.     

Synthesis and murine antineoplastic activity of bis[(carbamoyloxy)methyl] derivatives of pyrrolo[2,1-a]isoquinoline

The synthesis of 4,5-dihydropyrrolo[2,1-a]isoquinolines is reported. A key intermediate in the synthesis of 8-methoxy-4,5-dihydropyrrolo[2,1-a]isoquinolines, 6-hydroxy-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid (6), was prepared by using a regiospecific phenolic cyclization reaction. The P388 lymphocytic activity is reported for 1,2-bis(hydroxymethyl)-5,6-dihydro-8-methoxy-3-methylpyrrolo [2,1-a]isoquinoline bis(isopropylcarbamate) (11a), 1,2-bis(hydroxymethyl)-5,6-dihydro-8-methoxy-3-methylpyrrolo[2,1-a ]isoquinoline bis(cyclohexylcarbamate) (11b), 1,2-bis(hydroxymethyl)-5,6-dihydro-3-methylpyrrolo[2,1-a]isoqui nol ine bis(methylcarbamate) (13a), 1,2-bis(hydroxymethyl)-5,6-dihydro-3-methylpyrrolo [2,1-a]isoquinoline bis(ethylcarbamate) (13b), and 1,2-bis(hydroxymethyl)-5,6-dihydroxy-3-methylpyrrolo[2,1-a]isoq uin oline bis(cyclohexylcarbamate) (13c); all of the compounds were active. Compound 11a was tested in an expanded tumor panel and was shown to be active against B16 melanocarcinoma, CD8F1 mammary, L1210 lymphoid leukemia, colon 38, and MX-1 human tumor breast xenograft systems.     

Antitumor activity of 2(S)-5,2′,5′-trihydroxy-7,8-dimethoxyflavanone and its analogues

In an effort to increase of the antitumor activity of 2(S)-5,2',5'-trihydroxy-7,8-dimethoxyflavanone isolated fromScutellaria indica, we synthesized its analogues,II, III, andIV. They showed potent cytotoxicityin vitro against cancer cell lines, L1210, K562 and A549. On the basis of ED(50) values against the cancer cell lines,III exhibited about 2-7 times stronger activity thanI against various cell lines. We tested the antitumor activity of the analogues against Sarcoma 180 cellsin vivo and evaluated the structure-activity relationship. The antitumor activity appeared to be related to the hydrogen bond between carbonyl group at C-4 and hydroxyl group at C-5, in contrast to cytotoxic action.     

Cyclic guanidines: synthesis and antiplatelet activity of 4,6,7,8-tetrahydro-1H-imidazo[1,2-a]pyrazolo[3,4-d]pyrimidin-7-ones and 1,4,6,7,8,9-hexahydropyrazolo [3',4':4,5]pyrimido[2,1-c] [1,2,4]triazin-7-ones

A series of 4,6,7,8-tetrahydro-1H-imidazo[1,2-a]pyrazolo [3,4-d]pyrimidin-7-ones (1b-n) and 1,4,6,7,8,9-hexahydropyrazolo [3',4':4,5]pyrimido [2,1-c][1,2,4]triazin-7-ones (2a-d) has been synthesized. In view of their potential anti-aggregating activity the compounds were tested in vitro for inhibitory activity towards ADP- and collagen-induced aggregation of human platelets. Among the compounds studied, 8-benzyl-1-(2,5-dichlorophenyl)-4,6,7,8-tetrahydro-1H-imidazo [1,2-a]pyrazolo[3,4-d]pyrimidin-7-one (1n) exhibited the most favorable activity. The 2,5-dichlorophenyl side chain is an important lipophilic and/or steric pharmacophore.     

Synthesis and antiviral/antitumor activities of certain pyrazolo[3,4-d]pyrimidine-4(5H)-selone nucleosides and related compounds

Several pyrazolo[3,4-d]pyrimidine-4(5H)-selone ribonucleosides were prepared as potential antiparasitic agents. Treatment of 4-chloro-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)pyrazolo [3,4-d]pyrimidine (5a) with selenourea and subsequent deacetylation gave 1-beta-D-ribofuranosylpyrazolo[3,4-d] pyrimidine-4(5H)-selone (6a). A similar treatment of 3-bromo-4-chloro-1-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)pyrazolo [3,4-d]pyrimidine (5b) with selenurea, followed by debenzoylation, gave the 3-bromo derivative of 6a (6b). Glycosylation of persilylated 4-chloro-6-methyl-pyrazolo [3,4-d]pyrimidine (7) with tetra-O-acetylribofuranose (8) provided the key intermediate 4-chloro-6-methyl-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl) pyrazolo[3,4-d]pyrimidine (9). Ammonolysis of 9 gave 4-amino-6-methyl-1-beta-D-ribofuranosylpyrazolo[3,4-d]pyrimidine (10), whereas treatment with sodium hydroxide gave 6-methylallopurinol ribonucleoside (11a). Reaction of 9 with either thiourea or selenourea, followed by deacetylation, provided 6-methylpyrazolo[3,4-d]pyrimidine-4(5H)-thione ribonucleoside (11c) and the corresponding seleno derivative (11d), respectively. The structural assignment of these nucleosides was made on the basis of spectral studies. These compounds were tested in vitro against certain viruses and tumor cells. All the compounds except 11c exhibited significant activity against HSV-2 in vitro, whereas 11c exhibited the most potent activity against measles and has a very low toxicity. Compounds 6a, 6b, and 11d were found to be potent inhibitors of growth of L1210 and P388 leukemia in vitro.     

Structure and antipyretic-hypothermizing effect of various pyrazol/1,5-a/pyrimidines]

Structures of condensation products between 3-phenyl-5-aminopyrazole and ethyl ethoxymethylenacetoacetate and ethyl acetonoxalate are demonstrated, namely ethyl 2-phenyl-7-methylpyrazolo[1,5-a]pyrimidin-6-carboxylate and ethyl 2-phenyl-7-methylpyrazolo[1,5-a]pyrimidin-5-carboxylate. Studies on antipyretic and hypothermizing activity of the acid derived from the latter and of other compounds are reported.     

Synthesis and structure-activity relationship of cytotoxic 5,2′,5′-trihydroxy-7,8-dimethoxyflavanone analogues

Analogues of 2(S)-5,2′,5′-trihydroxy-7,8-dimethoxyflavanone, a naturally-occurring compound, which had been reported to have potent antitumor activity, were synthesized and examined for the cytotoxicity against three cancer cell lines. Among the intermediate chalcones and synthetic 5-hydroxy-7,8-dimethoxyflavanone analogues, (±)2′,5′-dibenzyloxy-5,7,8-trimethoxyflavanone exhibited about 2–8 times stronger activity than 2(S)-5,2′,5′-trihydroxy-7,8-dimethoxyflavanone against L1210, K562 and A549 cancer cell lines. In the structure-activity relationship, it is suggested that among analogues of 5-hydroxy-7,8-dimethoxyflavanone, the existence of two oxygenated groups ofpara-relation at C-2′ and C-5′ positions on flavanone Bring, may be necessary to exhibit effective cytotoxic activity.     

Antiprotozoal activity of 3'-deoxyinosine. Inverse correlation to cleavage of the glycosidic bond

Two nucleosides related to the known antiprotozoal agent 1-(beta-D-ribofuranosyl)-1,5-dihydro-4H-pyrazolo-[3,4-d]pyrimidine-4-one (allopurinol riboside, 1) were prepared and evaluated against Leishmania donovani, Trypanosoma cruzi, and Trypanosoma gambiense. 3'-Deoxyinosine (2) exhibited potent antiprotozoal activity against the three protozoal pathogens with minimal toxicity for host cells. It was found to be especially effective against the Columbia strain of T. cruzi reported to be resistant to 1. The antiprotozoal activity of 2 appeared to be inversely related to the rate of cleavage of the glycosidic bond, as shown by metabolic profiles of 2 in the various pathogenic hemoflagellates and host cells. Combining the key structural elements of 1 and 2 led to the synthesis of 1-(3-deoxy-beta-D-erythro-pentofuranosyl)-1,5-dihydro-4H-pyrazolo[3,4-d] pyrimidin-4-one (3'-deoxy-allopurinol riboside, 3). which was found to be inactive as an antiprotozoal agent.     

Synthesis and biological activity of 6-azacadeguomycin and certain 3,4,6-trisubstituted pyrazolo[3,4-d]pyrimidine ribonucleosides

Several 3,4,6-trisubstituted pyrazolo[3,4-d]pyrimidine ribonucleosides were prepared and tested for their biological activity. High-temperature glycosylation of 3,6-dibromoallopurinol with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose in the presence of BF3 X OEt2, followed by ammonolysis, provided 6-amino-3-bromo-1-beta-D-ribofuranosylpyrazolo-[3,4-d]pyrimidin-4(5H)-on e. Similar glycosylation of either 3-bromo-4(5H)-oxopyrazolo [3,4-d]pyrimidin-6-yl methyl sulfoxide or 6-amino-3-bromopyrazolo [3,4-d]pyrimidin-4(5H)-one, and subsequent ammonolysis, also gave 7a. The structural assignment of 7a was on the basis of spectral studies, as well as its conversion to the reported guanosine analogue 1d. Application of this glycosylation procedure to 6-(methylthio)-4(5H)-oxopyrazolo[3,4-d]pyrimidine-3-carboxamide gave the corresponding N-1 glycosyl derivative. Dethiation and debenzoylation of 16a provided an alternate route to the recently reported 3-carbamoylallopurinol ribonucleoside thus confirming the structural assignment of 16a and the nucleosides derived therefrom. Oxidation of 16a and subsequent ammonolysis afforded 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-carboxamide. Alkaline treatment of 15a gave 6-azacadeguomycin. Acetylation of 15a, followed by dehydration with phosgene, provided the versatile intermediate 6-amino-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-4(5H)-oxopyrazolo [3, 4-d]pyrimidine-3-carbonitrile. Deacetylation of 19 gave 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-carbonitrile. Reaction of 19 with H2S gave 6-amino-1-beta-D-ribofuranosyl-4(5H)-oxopyrazolo[3, 4-d]pyrimidine-3-thiocarboxamide. All of these compounds were tested in vitro against certain viruses and tumor cells. Among these compounds, the guanosine analogues 7a and 20a showed significant activity against measles in vitro and were found to exhibit moderate antitumor activity in vitro against L1210 and P388 leukemia. 6-Azacadeguomycin and all other compounds were inactive against the viruses and tumor cells tested in vitro.     

5,7-二取代吡唑并[1,5-a]嘧啶类化合物的合成及其抗肿瘤活性

目的设计并合成吡唑并[1,5-a]嘧啶类化合物,并评价其抗肿瘤活性。方法根据吡唑并[1,5-a]嘧啶类抗肿瘤药物的基本结构,设计了14个5-胺甲基-7-苯胺基吡唑并[1,5-a]嘧啶类化合物,并以丙二腈和原甲酸三乙酯为起始原料,经5步反应得到目标产物。采用MTT法,顺铂为阳性对照药,以Bel-7402和HT-1080为测试细胞株对目标化合物进行抗肿瘤活性评价。结果与结论合成了14个未见文献报道的新化合物,结构经MS、IR和1H-NMR确证。体外活性实验表明:化合物12显示出较好的抗癌活性。     

4-烷硫基-4-脱氧-4′-去甲表鬼臼毒素的合成和抗肿瘤活性

对4’-去甲表鬼臼毒素的C₄位进行化学修饰,合成和筛选了10个4-烷硫基-4-脱氧-4’-去甲表鬼臼毒素衍生物以进一步研究C₄位不同的原子和取代基与活性之间的关系及寻找结构简单、活性更强的抗肿瘤新药。4’-去甲表鬼臼毒素与硫醇在三氟化硼·乙醚或三氟乙酸存在下生成相应的硫醚,也可用硫醇与4β-溴-4-脱氧-4’-去甲表鬼臼毒素反应生成相应的硫醚。在体外筛选中,化合物10和12抑制L1210白血病细胞的活性与依托泊甙相当或更强,化合物9,10,12和15抑制KB细胞的活性与依托泊甙相当或更强。     

Design,synthesis and antitumor activity of C3/C3 bis-fluoroquonolones cross-linked with [1,2,4]triazolo[3,4-b] [1,3,4]thiadiazole

To contribute to the development of an efficient method for the conversion of antibacterial fluoroquinolones to antitumor fluoroquinolones, a series of C3/C3 bis-fluoroquinolone fused heterocycles cross-linked with a [1,2,4]-triazolo[3,4-b] [1,3,4]-thiadiazole core as a common bioisostere of two carboxylic acid groups was designed and synthesized as their hydrochloride salts. Structures were characterized by elemental analysis and spectral data and their in vitro antitumor activity against L1210, CHO and HL60 cell lines was screened by determination of their IC₅₀ values in the methylthiazole trazolium (MTT) assay. Two compounds were highly potent against the HL60 cell line and represent promising lead compounds for future development.     

Polyhydroxylated phenylacrylic acid derivatives as new anti-tumor agents

Preliminary evidence indicates that antitumor agents containing the o-dihydroxybenzene moiety exhibit enhanced antitumor activity toward malignant cells of high oxidative potential, such as melanoma cells. Based on this consideration, 11 hydroxybenzene acrylic acid derivatives of differing redox potential were prepared as potential substrates for the melanoma specific enzyme tyrosinase, that might exhibit general antitumor activity and enhanced cytotoxicity toward melanoma cells. Five of these compounds [alpha-cyano-beta-(4-hydroxyphenyl)-, alpha-cyano-beta-(3,4-dihydroxyphenyl)-, and alpha-cyano-beta-(3,4,5-trihydroxyphenyl)acrylic acid (THPPA), and 3,4-dihydroxy- and 3,4,5-trihydroxybenzalcyanoacetamide] were found to be substrates for tyrosinase with Km values from 0.08 to 4.13 mM and Vmax values from 0.18 to 3.02. These data indicate that as the number of hydroxy groups increases, the rate of oxidation increases, and that cyanoamides were faster reacting than corresponding cyanoacids, with dicyanides the least reactive. In contrast, cyanoamides were less effective as substrates than cyanoacids. In vitro studies showed all but two compounds were active against L1210 (IC50 range 21-980 microM), SK-MEL-28 (IC50 range 54-950 microM), and SK-MEL-30-3 (IC50 range 54-190 microM). Only THPPA was active in vivo against L1210 and B-16 melanoma.     

Synthesis and antitumor properties of pyrazolo [3,4-D] pyrimidine derivatives

Several new 5-substituted 1-phenylpyrazole [3,4-d] pyrimidine derivatives were synthesized and tested for antitumor activity. Compound 17, which has 3,4-dichlorophenyl moiety at N5 of the pyrazole pyrimidine ring, shows a strong activity against L-1210 leukemia (152%). On the other hand, compounds 15, 17 and 21 were the most active against sarcoma Sa-180. It was observed that many derivatives of pyrazole [3,4-d] pyrimidine possess different biological, especially antitumor properties [1-6, 9, 10].     

Synthesis of some 7-phenylpyrrolo[1,2-a]pyrimidine derivatives. III

2-Amino-4-phenylpyrrolyl-3-carbonitrile (I) was reacted with ethyl formylacetate sodium salt affording 1,4-dihydro-4-oxo-7-phenylpyrolo[1,2-a]pyrimidin-8-carbonitrile (II), which was alkylated with EtI to give (III), which in turn was hydrolyzed to (IV). Treatment of both (III) and (IV) with 99% H3PO4 at approximately 200 degrees gave 1,4-dihydro-1-ethyl-7-phenylpyrrolo-[1,2-a]pyrimidin-4-one (V) whose structure was ascertained by an unequivocal synthesis starting from (I) and diethyl ethoxymethylenmalonate. Compound (V) was prepared in order to test its pharmacological properties in comparison with 4,7-dihydro-4-ethyl-2-phenylpyrazolo[1,5-a]pyrimidin-7-one, which showed an antiinflammatory activity comparable to that of phenylbutazone and indomethacine, and which was found devoid of ulcerogenic properties.