2-Aryl-2,2-difluoroacetamide FKBP12 ligands: synthesis and X-ray structural studies.

[structure: see text] 2-Aryl-2,2-difluoroacetamido-proline and pipecolate esters are high affinity FKBP12 ligands whose rotamase inhibitory activity is comparable to that seen for the corresponding ketoamides. X-ray structural studies suggest that the fluorine atoms participate in discrete interactions with the Phe36 phenyl ring and the Tyr26 hydroxyl group, with the latter resembling a moderate-to-weak hydrogen bond.

Synthesis and antitumor activity of novel C-7 paclitaxel ethers: discovery of BMS-184476.

The preparation of C-7 paclitaxel ethers is described. Various substituted ethers were prepared via activation of the corresponding methylthiomethyl ether followed by alcohol addition. Variation of the C-7 ether group as well the 3' side chain position led to the discovery of a novel taxane, BMS-184476 (4), with preclinical antitumor activity superior to paclitaxel.

Synthesis of a novel C-10 spiro-epoxide of paclitaxel.

New analogues of paclitaxel (1a, active constituent of Taxol) were synthesized containing an epoxide at the C-10 position. The introduction of the epoxide was carried out by selective removal of the C10-acetate followed by protection of the C2'- and C7-hydroxyl groups. After oxidation to yield a ketone at the C10-position, this intermediate was reacted with dimethylsulfonium ylide. Deprotection and further manipulations provide the C10-spiro epoxide of paclitaxel (1b) and the corresponding C7-MOM ether (1c).

Synthesis of 7beta-sulfur analogues of paclitaxel utilizing a novel epimerization of the 7alpha-thiol group.

Paclitaxel analogues with a sulfur group at the 7beta position were required for SAR studies. Attempts to generate these compounds by displacing a 7alpha leaving group with sulfur nucleophiles were unsuccessful. Instead, these compounds were successfully prepared from a 7beta-thiol intermediate that was obtained by a base-catalyzed epimerization of the 7alpha-thiol derivative. The epimerization presumably proceeds through a thioaldehyde intermediate and exhibits the opposite stereochemical preference of its oxygen counterpart.

Synthesis of metabolically blocked paclitaxel analogues.

The stereospecific syntheses of the metabolically blocked 6-alpha-F, Cl, Br paclitaxel, and 6-alpha-F-10-acetyldocetaxel are described and in vitro and in vivo activity is presented.

Synthesis and antitumor activity of novel paclitaxel-chlorambucil hybrids.

The syntheses and antitumor activity of three paclitaxel-chlorambucil hybrids are presented. Hybrid 3 showed significant in vivo efficacy.

Structure-activity relationships study at the 3'-N position of paclitaxel. Part 2: synthesis and biological evaluation of 3'-N-thiourea- and 3'-N-thiocarbamate-bearing paclitaxel analogues.

The syntheses and preliminary biological evaluation of 3'-N-thiocarbamate- and 3'-N-thiourea-bearing paclitaxel analogues, 4a-f and 5a-e, are described. 3'-N-thiocarbamates 4a-e were found to be more potent than paclitaxel in both the tubulin polymerization assay and the in vitro cytotoxicity assay. Several derivatives of this class such as 4c, 4d, and 4e also exhibited some in vivo activity.

Synthesis of a paclitaxel isomer: C-2-acetoxy-C-4-benzoate paclitaxel.

A synthesis of the C-2-acetoxy-C-4-benzoate paclitaxel 2 is described. This analog has the substituents at C-2 and C-4 transposed. The key steps in the synthesis include the sequential use of Red-Al as reducing agent for the regioselective reduction of the C-2 benzoate and the C-4 acetoxy within the baccatin core. Iso-paclitaxel 2 was considerably less potent than paclitaxel in tubulin polymerization and in vitro cytotoxicity assays.

Nicotinic cholinoceptor-mediated excitatory postsynaptic potentials in rat nucleus ambiguus.

In rat brainstem slice preparations, intracellular recording from neurons (n = 39) in the compact formation of the nucleus ambiguus (AMBc) revealed spontaneous and miniature excitatory postsynaptic potentials (EPSPs; n = 11) that, along with acetylcholine-induced depolarization, were enhanced by physostigmine (10 microM; n = 2) and blocked by dihydro-beta-erythroidine 1-5 pmol (n = 4). Retrograde neuronal tracing combined with choline acetyltransferase immunocytochemistry demonstrated that the AMBc receives a projection from a subpopulation of cholinergic neurons in the zona intermedialis reticularis parvicellularis. Electrical stimulation of this region in slices evoked fast EPSPs in AMBc neurons (n = 23) that were inhibited by dihydro-beta-erythroidine 2-5 pmol (n = 8), but not by methscopolamine 1 pmol (n = 2). The present findings strongly support the existence of a cholinergic nicotinic synapse mediating fast transmission in brainstem vagal motoneurons.

Activity of C-7 substituted cyclic acetal derivatives of mitomycin C and porfiromycin against hypoxic and oxygenated EMT6 carcinoma cells in vitro and in vivo.

A series of cyclic acetal derivatives of mitomycin C (MC) and porfiromycin (POR) were tested for their ability to kill hypoxic and oxygenated EMT6 tumor cells. Amino methyl acetal and thioacetal substitutions at C-7 of MC and POR dramatically increased the cytotoxicity of the compounds to hypoxic EMT6 tumor cells in vitro but had little effect on the aerobic toxicities. In contrast, a methyl substitution at N1a markedly decreased the aerobic cytotoxicities of the compounds but did not alter the hypoxic cytotoxicities. The POR acetal, BMY-42355, had the largest differential between hypoxic and aerobic cytotoxicities yet observed among MC analogs. Preliminary studies in mice showed that BMY-42355 had good antineoplastic activity when used alone or in combination with radiation and was less toxic than POR; the therapeutic ratio of this compound in these initial studies was higher than those of either MC or POR.

New hydrazone derivatives of adriamycin and their immunoconjugates--a correlation between acid stability and cytotoxicity.

New N-substituted hydrazine linkers were synthesized and their hydrazone derivatives of adriamycin were prepared. These functionalized adriamycin derivatives were conjugated with a monoclonal antibody, 5E9. The release rate of adriamycin from the hydrazones and from some of the conjugates was studied, and their relationship to the IC50's of the conjugate against 5E9-positive Daudi cells was investigated.

Second generation analogs of etoposide and mitomycin C.

Programs directed towards the selection of etoposide and mitomycin C analogs which exhibit superior activity, reduced toxicity and improved pharmaceutics have met with partial success. Etopofos (BMY 40481) has been chosen for development as a prodrug of etoposide possessing superior pharmaceutical properties. BMY 25067, an analog of mitomycin C, is also under development based on its improved activity profile, acceptable toxicology profile and possibly different mechanism of action.

Structure-activity comparison of mitomycin C and mitomycin A analogues (review).

Over 600 analogues of mitomycin C (MMC) have been made in the past and more recently a number of Mitomycin A (MMA) derivatives have been prepared. Since many of the MMA type had the same organic side chain at the 7-position as previously prepared MMC analogues it was of interest to see if the biological effects of MMCs could predict for those of MMAs. Using the P388 leukemia model it was possible to compare the activity of 27 matched pairs and the potency of 24 pairs. It was found that antitumor effects did not correlate but that MMAs were significantly more potent than MMCs. These findings were duplicated in tests of 7 pairs against subcutaneously implanted B16 melanoma. We conclude that any MMA derivative would have a high likelihood of being more potent than its MMC equivalent but that its antitumor effects must be independently determined since they cannot be predicted from the results with MMC analogs.

Reassignment of the structure for the antitumor agent RR-150.

7-Cysteaminomitosane (RR-150) has been reported to be superior to mitomycin C against P388 leukemia and B-16 melanoma in mice and is less leukopenic. Studies reported here indicated the absence of a free thiol group in RR-150 and therefore the structure was incorrectly assigned. Reaction of mitomycin A with either 2-aminoethanethiol or cystamine gave the same disulfide, 7-N,7'-N'-dithiodiethylenedimitomycin C, which is the newly proposed structure for RR-150. Attempts to produce 7-cysteaminomitosane by reduction of the disulfide have not succeeded because of its apparent instability.

Evidence that L-sucrose is resistant to hydrolysis catalyzed by jejunal brush border enzymes.

The sucrase-isomaltase complex of the intestinal brush border membrane (BBM) catalyzes the hydrolysis of sucrose. The stereospecificity of this enzyme, however, is not known. To investigate this, BBM of hamster jejunum was incubated with D-sucrose or L-sucrose, and the reaction mixture was analyzed using a gas-liquid chromatograph. It was found that D-sucrose was hydrolyzed to its monomers, but L-sucrose remained unhydrolyzed. It is concluded that the sucrase-isomaltase of intestinal BBM of hamster jejunum does not hydrolyze L-sucrose and therefore this enzyme is stereospecific.

Effects of isoproterenol on hydroxysteroid dehydrogenases of preputial gland of male rats.

Histochemical observations were made on the activities of 17 beta-hydroxysteroid dehydrogenase (HSDH), 3 beta-hydroxysteroid dehydrogenase (3 beta-HSDH) and 3 oC-hydroxysteroid dehydrogenase (3 oC-HSDH) in the preputial glands of normal and isoproterenol treated animals. Observed decrease in the activities of all the three HSDH's are correlated with the possibility of decreased biological effectiveness of circulating steroids after isoproterenol treatment.