Heterocycle-containing retinoids. Discovery of a novel isoxazole arotinoid possessing potent apoptotic activity in multidrug and drug-induced apoptosis-resistant cells.

In a search for retinoic acid (RA) receptor ligands endowed with potent apoptotic activity, a series of novel arotinoids were prepared. Because the stereochemistry of the C9-alkenyl portion of natural 9-cis-RA and the olefinic moiety of the previously synthesized isoxazole retinoid 4 seems to have particular importance for their apoptotic activity, novel retinoid analogues with a restricted or, vice versa, a larger flexibility in this region were designed and prepared. The new compounds were evaluated in vitro for their ability to activate natural retinoid receptors and for their differentiation-inducing activity. Cytotoxic and apoptotic activities were, in addition, evaluated. In general, these analogues showed low cytotoxicity, with the restricted structures being slightly more active than the more flexible ones. As an exception, however, the isoxazole retinoid 15b proved to be particularly able to induce apoptosis at concentrations <5 microM, showing a higher activity than the classical retinoids such as all-trans-RA, 13-cis-RA, and 9-cis-RA and the previously described synthetic retinoid 4. 15b also exhibited a good affinity for the retinoid receptors. Interestingly, another important property of 15b was its ability to induce apoptosis in the HL60R multidrug-resistant (MDR) cell line, at the same concentration as is effective in HL60. Therefore, 15b represents a new retinoid possessing high apoptotic activity in an MDR cell line. The ability of 15b to act on K562 and HL60R cells suggests that this compound may have important implications in the treatment of different leukemias, and its structure could offer an interesting model for the design of new compounds endowed with apoptotic activity on MDR- and retinoid-resistant malignancies.

Effects of two-carbon bridge region methoxylation of benztropine: discovery of novel chiral ligands for the dopamine transporter.

6-Methoxylated and 8-oxygenated benztropines were prepared and evaluated for their DAT and SERT activity (binding and uptake inhibition). Methoxylation at the two-carbon bridge of benztropine produced a novel class of potent and selective DAT ligands. An interesting enantioselectivity was also observed for this new class of chiral benztropines. The inactivity of the 8-oxygenated analogues seems to point out that, unlike cocaine and its analogues, interactions of benztropine ligands with DAT may be strongly governed by the nitrogen atom.

Programmed cell death (PCD) associated with the stilbene motif of arotinoids: discovery of novel apoptosis inducer agents possessing activity on multidrug resistant tumor cells.

Considering that the stereochemistry of the C9-C10 alkenyl portion of natural 9-cis-RA, as the one of the olefinic moiety of the previously described isoxazole retinoid 4, seems of particular importance for their apoptotic activity, we prepared a novel class of TTNPB analogues bearing both the cis or trans configuration of the alkenyl portion. The compounds were evaluated in vitro for their cytotoxic and apoptotic activities. We discovered that the cis-TTNPB 9c possesses apoptotic activity comparable with that of the retinoid 4. Moreover, the amino arotinoid 16c showed potent apoptotic activity in HL60 promyelocytic leukemia cells. Interestingly, 16c proved to be a particularly potent apoptosis-inducing agent active in multidrug resistant (MDR) cell lines. Therefore, to the best of our knowledge, 16c may represent the first known aminoarotinoid endowed with potent apoptotic activity in MDR cells. Taken together, these results seem to point out that the cis-stilbene motif of arotinoids may be at least an important feature in conferring cytotoxic and apoptotic activity to this class of compounds.

Structure-activity relationship studies of novel heteroretinoids: induction of apoptosis in the HL-60 cell line by a novel isoxazole-containing heteroretinoid.

In a search for retinoic acid receptor (RAR and RXR)-selective ligands, a series of isoxazole retinoids was synthesized and evaluated in vitro in transcriptional activation and competition binding assays for RARs and RXRs. In addition, these compounds were evaluated for their differentiating, cytotoxic, and apoptotic activities. In general, these derivatives showed scarcely any binding affinity and were not active in the transcriptional assay. However, among these isoxazole derivatives, the cis-isomer 14b was identified as a potent inducer of apoptosis, and its activity was found to be 6.5 and 4 times superior than that of 13-cis- and 9-cis-retinoic acids, respectively. On the other hand, compound 13b, which has the trans stereochemistry at the double bond, was found not to be active in the apoptotic assay, but it was endowed with appreciable differentiating activity. Therefore, it seems that the different stereochemistry of the double bond may be associated with a different biological activity: potent apoptotic activity for the cis-isomer but differentiating activity for the trans structure. This biological behavior was found, at least in part, for the 9-cis- and 13-cis-retinoic acids with respect to the all-trans-retinoic acid. Thus, structure 14b could offer an interesting model for the design of new compounds endowed with apoptotic activity.

Two-carbon bridge substituted cocaines: enantioselective synthesis, attribution of the absolute configuration and biological activity of novel 6- and 7-methoxylated cocaines.

In an effort to learn more about the general structure-activity relationships of cocaine with the aim to elucidate those structural features that might confer antagonistic properties to such analogues, we describe herein our synthetic efforts to prepare two-carbon bridge functionalized (methoxylated and hydroxylated) analogues. Our approach makes use of a modification of the classical Willstatter synthesis of cocaine: Mannich type cyclization of acetonedicarboxylic acid monomethyl ester with methylamine hydrochloride and 2-methoxysuccindialdehyde in a citrate buffer solution afforded the 6- and 7-substituted 2-carbomethoxy-3-tropinones 3a,b and 4a,b in approximate yields of 64%. Reduction of the (+/-)-tropinone derivatives was performed with sodium amalgam in a sulfuric acid solution to afford a mixture of (+/-)-methoxyecgonine and (+/-)-methoxypseudoecgonine derivatives 5, 11 and 6, 7, 12, 13. Benzoylation of these alcohols yielded the desired cocaine and pseudococaine-like compounds 8, 14 and 9, 10, 15, 16. Additionally, we show that enzymatic hydrolysis of these cocaine analogues using pig liver esterase (PLE) affords a practical means for achieving their chemical resolution. The enantiomers of the methoxycocaine analogues were also prepared starting from chiral (+)- and (-)-6-methoxytropinone. All new analogues were examined for their ability to displace [3H]mazindol binding and to inhibit high-affinity uptake of [3H]dopamine into striatal nerve ending (synaptosomes). It appeared evident that methoxylation of the cocaine two-carbon bridge provides compounds of particular interest: the Ki for the binding of the methoxypseudococaines is about two to four times smaller than the Ki for inhibition of dopamine uptake, thus enabling these compounds capable of countering the effects of cocaine to some extent.

3,6-Disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles: synthesis and evaluation for antimicrobial and antiviral activity. III.

A series of novel 3,6-disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole derivatives was prepared and tested to evaluate their antimycotic, antibacterial and anti-HIV-1 activities. The reaction of thiocarbohydrazide with carboxylic acids at the melting temperature allows an improved preparation of the 5-substituted 4-amino-3-mercapto-1,2,4-triazole heterocycles which in turn allows an easier preparation of the 1,2,4-triazolo[3,4-b] [1,3,4]thiadiazole ring system. All tested compounds didn't show any significant activity.

3,6-Disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles: synthesis, antimicrobial and antiviral activity. II.

A series of novel 3,6-disubstituted 1,2,4-triazolo[3,4-b][1,3,4] thiadiazole derivatives was prepared and tested to evaluate their antimycotic and antibacterial activities. Anti-HIV-1 activity has also been investigated. Among the test compounds, derivatives 10a-14a and 16c showed anti-HIV-1 activity at concentrations slightly below those cytotoxic. Substitutions at 3 and 6 positions seems to be important in lowering the cytotoxicity of compounds.

Synthesis and pharmacological properties of 6-substituted 3-(pyridine-4-yl)-1,2,4-triazole [3,4-b][1,3,4]thiadiazoles.

A number of new 6-substituted 3-(pyridine-4-yl) 1,2,4-triazole[3,4-b][1,3,4]thiadiazoles were synthesized and evaluated for their pharmacological activity. Some of them exhibited moderate MAO, antimalarial and in vitro antitumor activity.

[Synthesis of 4(2H-1,2,3-triazol-2-yl)pyrimidines]. / Sintesi di 4-(2H-1,2,3-triazol-2-il)pirimidine.

4-(2H-1,2,3-triazol-2-yl)pyrimidines were synthesized. The title compounds tested for analgesic and antiinflammatory activity did not show any significant activity.