Synthesis and antitumor activity of 20(S)-camptothecin derivatives: carbamate-linked, water-soluble derivatives of 7-ethyl-10-hydroxycamptothecin

Novel 36 derivatives (6), bonding the phenolic hydroxyl group of 7-ethyl-10-hydroxycamptothecin (4) with diamines through a monocarbamate linkage, were synthesized and their antitumor activity was evaluated in vivo. The derivatives were soluble in water as their HCl salts with the E lactone ring intact and exhibited significant antitumor activity. One of the derivatives, 6-27 showed excellent activity against L1210 leukemia and other murine tumors. The structure of its hydrochloride trihydrate (CPT-11) was determined by spectroscopic and crystallographic methods.     

四(对-乙酰氧醚-10-羟基喜树碱)苯基卟啉的合成及结构表征

设计并合成了一种卟啉类光敏剂与抗癌药羟基喜树碱通过共价键相连的四(对-乙酰氧醚-10-羟基喜树碱)苯基卟啉化合物. 通过紫外光谱、 红外光谱、 核磁氢谱和质谱分析等手段对其结构进行了表征. 在癌症治疗过程中目标化合物中2种药物可能起到一定的协同效应.     

Epoxides,cyclic sulfites,and sulfate from natural pentacyclic triterpenoids: theoretical calculations and chemical transformations

Several triterpenic derivatives, with the A-ring functionalized, were semisynthesized from oleanolic and maslinic acids. The reactivities of sulfites, sulfate, and epoxides in these triterpene compounds were investigated under different reaction conditions. Moreover, contracted A-ring triterpenes (five-membered rings) were obtained, by different treatments of the sulfate 7. From the epoxide 8, deoxygenated and halohydrin derivatives were semisynthesized with several nucleophiles. Ozonolysis and Beckmann reactions were used to yield 4-aza compounds, from five-membered ring olanediene triterpenes. The X-ray structure of sulfate 7 is given and compared with density functional theory geometries. Theoretical (13)C and (1)H chemical shifts (gauge-invariant atomic orbital method at the B3LYP/6-31G*//B3LYP/6-31G* level) and (3)J(H,H) coupling constants were calculated for compounds 5-9 and 34-36, identifying the (R)- or (S)-sulfur and alpha- or beta-epoxide configurations together with 4-aza or 3-aza structures.     

Synthesis and antitumor activity of duocarmycin derivatives: a-ring pyrrole compounds bearing 5-membered heteroarylacryloyl groups.

A series of A-ring pyrrole compounds of duocarmycin bearing 5-membered heteroarylacryloyl groups (thienylacryloyl and pyrrolylacryloyl) and heteroarylcarbonyl groups were synthesized and evaluated for in vitro anticellular activity against HeLa S3 cells and in vivo antitumor activity against murine sarcoma 180 in mice. Most of the thienylacrylates displayed in vitro anticellular activity equivalent to 4'-methoxycinnamates. Among the 8-O-[(N-methylpiperazinyl)carbonyl] derivatives of methoxy-thienylacrylates, compound 11b, having 4'-methoxy-2'-thienylacryloyl as segment-B (Seg-B), showed remarkably potent antitumor activity and low peripheral blood toxicity in vivo, which were equal to those of 8-O-[(N-methylpiperazinyl)carbonyl] derivatives of 4'-methoxycinnamates, compared with the A-ring pyrrole derivatives having the trimethoxyindole skeleton in Seg-B. On the other hand, the 2'-pyrrolylacrylates having a double bond as spacer showed 10(2)- to 10(3)-fold stronger anticellular activity than 2'-pyrrolecarboxylates (IC50 < 0.3 nM, 72 h-exposure). The 8-O-acetate and 8-O-[(N-methylpiperazinyl)carbonyl] derivatives of 2'-pyrrolylacrylates exhibited an antitumor effect at a lower dose compared with the 8-O-[(N-methylpiperazinyl] derivatives of 4'-methoxycinnamate (1j). Moreover, it was expected that the antitumor activity would be increased by the strength of the extra hydrogen bond formed between the nitrogen of the pyrrole amido group and DNA, owing to the increase of the number of N-methyl-2'-pyrrolecarboxamide units. However, 2'-pyrrolylacrylates having three N-methyl-2'-pyrrolecarboxamide units showed nearly equal antitumor activity to 2'-pyrrolylacrylates having only one N-methyl-2'-pyrrolecarboxamide unit.     

Heterocyclic-fused benzopyrans as cannabinoid analogues

A series of A-ring heterocyclic analogues of tetrahydrocannabinol were investigated. Chromanones 1a and 1b were functionalized by formylation with base and ethyl formate to give 6a and 6b. These formylketones were reacted with hydrazine, and Phenylhydrazine to give pyrazoles 7a,b,e , and f , respectively. When 6a and 6b were reacted wtih methylhydrazine, mixtures of methyl isomers 7c and 8a and 7d and 8b formed in a ratio of 1:2.5. Isoxazoles 10a and 10b formed similarly when hydroxylamine was used as the condensing agent. Attempts to prepare the pyrimidine derivatives 11 were thwarted by the rearrangements of 6a and 6b to chromenones 12a and 12b.     

Determination of Camptothecin and 10-Hydroxycamptothecin in Camptotheca acuminata by LC-ESI-MS/MS

A rapid and sensitive liquid chromatography-tandem mass spectrometry method with multiple reaction monitoring was developed for the simultaneous determination of camptothecin and 10-hydroxycamptothecin in Camptotheca acuminata. The separation of camptothecin and 10-hydroxycamptothecin was performed on an Agilent Eclipse XDB-C18 column with a mixture of methanol and water (1:1, v/v) containing 0.2% formic acid as a mobile phase. The limits of detection of camptothecin and 10-hydroxycamptothecin were 4.0 ng/mL and 7.0 ng/mL (S/N = 3), respectively. Analysis took 10 minutes, making the method suitable for rapid determination of camptothecin and 10-hydroxycamptothecin in C. acuminata.     

Determination of camptothecin and 10-hydroxycamptothecin in human plasma using polymer monolithic in-tube solid phase microextraction combined with high-performance liquid chromatography

A biocompatible in-tube solid-phase microextraction (SPME) device was used for the direct and on-line extraction of camptothecin and 10-hydroxycamptothecin in human plasma. Biocompatibility was achieved through the use of a poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column for extraction. Coupled to high performance liquid chromatography (HPLC) with UV detection, this on-line in-tube SPME method was successfully applied to the simultaneous determination of camptothecin and 10-hydroxycamptothecin in human plasma. The calculated detection limits for camptothecin and 10-hydroxycamptothecin were found to be 2.62 and 1.79 ng/mL, respectively. The method was linear over the range of 10–1000 ng/mL. Excellent method reproducibility was achieved, yielding RSDs of 2.49 and 1.59%, respectively. The detection limit (S/N=3) of camptothecin was found to reach 0.1 ng/mL using fluorescence detection. The proposed method was shown to cope robustly with the extraction and analysis of camptothecin and 10-hydroxycamptothecin in plasma samples.     

Preparation of a 24-nor-1,4-dien-3-one triterpene derivative from betulin: a new route to 24-nortriterpene analogues

A new route to 24-nortriterpene derivatives with 2-hydroxy-Delta(1,4)-cyclohexadien-3-one A-rings from triterpene precursors has been demonstrated beginning with betulin to prepare derivatives of betulinic acid. The key steps in the transformation are a Suárez cleavage of the A-ring with a subsequent SmI(2)-mediated pinacol-type coupling to reclose the A-ring following removal of the C-24 carbon by oxidative cleavage.     

葛根素衍生物的合成、表征及衍生化反应机理

合成了葛根素的7,4'-二丙基(Ⅰ), 7-单丙基(Ⅱ)和4'-单丙基(Ⅲ)三种取代衍生物. 其中7-丙基葛根素Ⅱ属于新型取代衍生物; 变温1H NMR和理论计算结果表明, 在300 K时, 葛根素和4'-丙基葛根素(Ⅲ)以单一构型存在; 而7,4'-二丙基葛根素(Ⅰ)和7-丙基葛根素(Ⅱ)则存在两种核磁可分辨的旋转异构体, 当温度升至330 K时, 两种异构体可以相互转化; 通过对比分析葛根素及其衍生物脱质子产物的紫外可见吸收光谱并结合理论计算, 确定了A环上7位酚羟基比B环上4'位酚羟基先脱去质子, 并由此进一步阐明了葛根素衍生化反应机理以及在抗氧化作用中可能的活性位点和结构活性关系.     

Synthesis of novel hapten derivatives of 1alpha,25-dihydroxy-vitamin D3 and its 20-epi analogue

Hapten derivatives of 1alpha,25-dihydroxyvitamin D(3) and its 20-epimer were synthesized and conjugated to a carrier protein for raising polyclonal antibodies. The haptens were linked through spacers at C-16, thereby exposing both the A-ring and the side chain of the molecules, to maximize antibody specificity. The spacers were introduced via stereoselective hydroboration of 16-ene intermediates as the key step. In immunoassays, the antibodies raised toward the natural hormone were selective to this compound over derivatives with modifications in the A-ring or the side chain. The antibodies toward the 20-epimer, however, were unable to recognize modifications in the side chain.     

A novel and stereoselective synthesis of 7α-alkynylestra-1,3,5(10)-triene-3,17β-estradiol

Different stereoselective synthetic routes for the preparation of 7α/β-substituted estradiol derivatives, that is, 7α-alkynylestra-1,3,5(10)-triene-3,17β-estradiol (13) and its 17β-acetate derivative (14), are explored. These steroids are key starting materials for Pd-catalyzed Sonogashira cross-coupling reactions to yield potential estrogen receptor (ER) antagonists, ER-based imaging ligands and other multi-functional agents. Initial preparation of 7α-alkynyl nortestosterone derivatives followed by various approaches to aromatize the A-ring, failed. Instead, stereoselective 7α-cyanation before A-ring aromatization, followed by 7α-cyano reduction to the 7α-aldehyde, dibromomethylenation and dehydrobromination of the aldehyde, gave the desired 7α-alkynyl derivatives 13 and 14 in good yield.     

Characterization of prednisone, prednisolone and their metabolites by gas chromatography-mass spectrometry

Human urinary metabolites of the synthetic corticosteroids prednisone and prednisolone were detected in the course of gas chromatographic steroid profiling as methoxime-trimethylsilyl derivatives. Metabolites were provisionaly identified by combined gas chromatography-mass spectrometry. The major metabolites were 11-keto/11-hydroxy conversion products, 20-hydroxy and 4,5-dihydro analogues of the parent drugs. Cortisone, 6-hydroxy and fully saturated A-ring compounds were minor metabolites. Retention indices and mass spectral data are presented.     

Synthesis and antitumor activity of 9-methyl-10-hydroxycamptothecin

A novel camptothecin analogue, 9-methyl-10-hydroxycamptothecin （4）, was unexpectedly synthesized from 10-hydroxycamptothecin in two steps. The key step included an efficient Mannich-type reaction. The overall yield was 47.2%. An ether analogue of 4, 9-methyl-10-benzylaminomethoxycamptothecin （5）, was also prepared. These new camptothecin analogues were evaluated for in vitro cytotoxicity against four human cancer cell lines, and exhibited more potent antitumor activities than contrals camptothecin and topotecan against several cancer cells.     

Solution kinetics of CC-1065 A-ring opening: substituent effects and general acid/base catalysis

pH-rate studies were carried out on 2-substituted derivatives of the CC 1065 A-ring over the range of pH 5 to 0. The goals were to document the presence of general-acid-catalyzed cyclopropyl ring opening near neutrality and to assess the role of the 2-substituent on the rate of nucleophile trapping by the cyclopropyl ring. Our studies show that the cyclopropyl group undergoes reversible general-acid/base-catalyzed trapping of chloride nucleophiles above pH 4. This finding implies that the general-acid-catalyzed alkylation of DNA minor groove by the A-ring is feasible. pH-rate studies also showed that the 2-substituent does not influence the pKa of the protonated carbonyl of the A-ring (pKa approximately 1) and has relatively little effect on the rate of nucleophile trapping. This finding is consistent with calculations that show the fused pyrrolo ring as the source of carbonyl oxygen electron density. The 2-nitrogen, on the other hand, only releases electrons to the carbonyl of the 2-substituent and does not greatly influence trapping of nucleophiles by the A-ring cyclopropyl group.     

Cal-B-catalyzed alkoxycarbonylation of a-ring stereoisomeric synthons of 1alpha,25-dihydroxyvitamin D3 and 1alpha,25-dihydroxy-19-nor-previtamin D3: a comparative study. first regioselective chemoenzymatic synthesis of 19-nor-A-ring carbonates

A comparative study of alkoxycarbonylation processes of both 19-nor-A-ring and A-ring stereoisomers of 1alpha,25-dihydroxyvitamin D3 analogues catalyzed by Candida antarctica lipase B (CAL-B) has been described. The presence of the methyl group in the A-ring at C-2, as in 3-6, has a determining role in the regioselectivity of the biocatalysis, mainly allowing the hydroxyl group at C-5 position to react. For the 19-nor-A-ring stereoisomers 7-10, which lack the C-2 methyl group, the configurations at C-3 and C-5 have a high influence in the selectivity exhibited by CAL-B. Thus, each couple of enantiomers showed opposing regioselectivities depending on the C-3 configuration. When C-3 possesses an (S)-configuration, enzymatic alkoxycarbonylations took place at the C-5-(R) or C-5-(S) hydroxyl groups. However, if the chiral centers at C-3 are (R), CAL-B alkoxycarbonylated the C-3-(R) hydroxyl group independently of the configuration at C-5. The corresponding carbonates are useful A-ring precursors of 1alpha,25-dihydroxyvitamin D3 analogues, selectively modified at the C-1 or C-3 positions. In addition, an improved synthesis of cis A-ring synthons 5 and 6 is described using a Mitsunobu methodology.     

Polymeric micelle systems of hydroxycamptothecin based on amphiphilic N-alkyl-N-trimethyl chitosan derivatives

This research investigated the possible utilization of amphiphilic N-octyl-N-trimethyl chitosan (OTMCS) derivatives in solublization and controlled release of 10-hydroxycamptothecin (10-HCPT), a hydrophobic anticancer drug. The release behavior of the 10-HCPT-OTMCS micelles was measured and compared to that of a commercial 10-HCPT lyophilized powder in vitro and in vivo. This research also examined the effects of chemical structure of the chitosan derivatives and the micellar preparation conditions on the encapsulation efficiency, drug loading content, and particle size of the polymeric micelles. The results showed that these chitosan derivatives were able to self-assemble and form spherical shape polymeric micelles with an average particle size range of 24–280 nm and a drug loading content of 4.1–32.5%, depending on the modified structures and loading procedures. The solubility of 10-HCPT in aqueous fluid was increased about 80,000-fold from 2 ng/ml in water to 1.9 mg/ml in OTMCS micellar (degree of octyl and trimethyl substitution is 8% and 54%, respectively) solution. In addition, OTMCS was able to modulate the in vitro release of 10-HCPT and improve its pharmacokinetic properties and lactone ring stability in vivo. These data suggested the possible utilization of the amphiphilic micellar chitosan derivatives as carriers for hydrophobic drugs for improving their delivery and release properties.     

Sulfonyl-stabilized oxiranyllithium-based approach to polycyclic ethers. Convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin

Convergent synthesis of the ABCDEF-ring system of yessotoxin and adriatoxin, marine polycyclic ether toxins causative of diarrheic shellfish poisoning, has been accomplished. The A-ring fragment was constructed by coupling of an appropriately functionalized sulfonyl-stabilized oxiranyl anion and a triflate prepared from an erythritol derivative. An iterative protocol of the oxiranyl anion strategy was also applied for the construction of the DEF-ring fragment. The triflate derivatives of the A-ring and the DEF-ring fragments were connected with lithium acetylide. The resulting acetylene derivative was further transformed into the hexacyclic ABCDEF fragment via oxidation of the acetylene unit to 1,2-diketone, double methyl acetal formation, and reductive etherification.     

Anticancer effect of A-ring or/and C-ring modified oleanolic acid derivatives on KB, MCF-7 and HeLa cell lines

New A-ring or/and C-ring modified methyl oleanolate derivatives were prepared. New simple method of synthesis of 3,12-diketone (3) from methyl oleanonate (2) was worked out. The obtained new compounds were tested for cytotoxic activity on KB, MCF-7 and HeLa cell lines. The derivatives had acetoxy, oxo or hydroxyimino function at the C-3 position and in some cases oxo, hydroxyimino or acyloxyimino group at the C-12 position. Almost all of the compounds showed strong cytotoxic activity, higher than unchanged oleanolic acid. The most active substances turned out to be the derivatives with acyloxyimino function, especially 4 and 8d.