Design and synthesis of bridged piperidine and piperazine isosteres.

We have developed versatile methods toward the synthesis of a variety of piperidine/piperazine bridged isosteres of pridopidine. The compounds were assessed against the D2 receptor in agonist and antagonist modes and against the D4 receptor in agonist mode. hERG Binding and the ADME profiles were studied.

Design and synthesis of novel N-sulfonyl-2-indoles that behave as 5-HT6 receptor ligands with significant selectivity for D3 over D2 receptors.

All clinically-used antipsychotics display similar affinity for both D2 (D2R) and D3 (D3R) receptors, and they likewise act as 5-HT2A receptor antagonists. They provide therapeutic benefit for positive symptoms, but no marked or consistent improvement in neurocognitive, social cognitive or negative symptoms. Since blockade of D3 and 5-HT6 (5-HT6R) receptors enhances neurocognition and social cognition, and potentially improves negative symptoms, a promising approach for improved treatment for schizophrenia would be to develop drugs that preferentially act at D3R versus D2R and likewise recognize 5-HT6R. Starting from the high affinity 5-HT6R ligands I and II, we identified compounds 11a and 14b that behave as 5-HT6R ligands with significant selectivity for D3R over D2R.

Constrained (l-)-S-adenosyl-l-homocysteine (SAH) analogues as DNA methyltransferase inhibitors.

Potent SAH analogues with constrained homocysteine units have been designed and synthesized as inhibitors of human DNMT enzymes. The five membered (2S,4S)-4-mercaptopyrrolidine-2-carboxylic acid, in 1a, was a good replacement for homocysteine, while the corresponding six-member counterpart was less active. Further optimization of 1a, changed the selectivity profile of these inhibitors. A Chloro substituent at the 2-position of 1a, compound 1d, retained potency against DNMT1, while N(6) alkylation, compound 7a, conserved DNMT3b2 activity. The concomitant substitutions of 1a at both 2- and N(6) positions reduced activity against both enzymes.

SAR around (l)-S-adenosyl-l-homocysteine, an inhibitor of human DNA methyltransferase (DNMT) enzymes.

The inhibitory activity of base-modified SAH analogues and the specificity of inhibiting human DNMT1 and DNMT3b2 enzymes was explored. The 6-amino group was essential while the 7-N of the adenine ring of SAH could be replaced by CH- without loss of activity against both enzymes. The introduction of small groups at the 2-position of the adenine moiety favors DNMT1 over DNMT3b2 inhibition whereas alkylation of the N(6)-amino moiety favors the inhibition of DNMT3b2 enzyme.

Structure-Based Design of a Eukaryote-Selective Antiprotozoal Fluorinated Aminoglycoside.

Aminoglycosides (AG) are antibiotics that lower the accuracy of protein synthesis by targeting a highly conserved RNA helix of the ribosomal A-site. The discovery of AGs that selectively target the eukaryotic ribosome, but lack activity in prokaryotes, are promising as antiprotozoals for the treatment of neglected tropical diseases, and as therapies to read-through point-mutation genetic diseases. However, a single nucleobase change A1408G in the eukaryotic A-site leads to negligible affinity for most AGs. Herein we report the synthesis of 6'-fluorosisomicin, the first 6'-fluorinated aminoglycoside, which specifically interacts with the protozoal cytoplasmic rRNA A-site, but not the bacterial A-site, as evidenced by X-ray co-crystal structures. The respective dispositions of 6'-fluorosisomicin within the bacterial and protozoal A-sites reveal that the fluorine atom acts only as a hydrogen-bond acceptor to favorably interact with G1408 of the protozoal A-site. Unlike aminoglycosides containing a 6'-ammonium group, 6'-fluorosisomicin cannot participate in the hydrogen-bonding pattern that characterizes stable pseudo-base-pairs with A1408 of the bacterial A-sites. Based on these structural observations it may be possible to shift the biological activity of aminoglycosides to act preferentially as antiprotozoal agents. These findings expand the repertoire of small molecules targeting the eukaryotic ribosome and demonstrate the usefulness of fluorine as a design element.

Functionalized glycomers as growth inhibitors and inducers of apoptosis in human glioblastoma cells.

The effects of functionalized aryl beta-D-glycopyranosides (glycomers) on the proliferation, survival, and apoptosis of human glioblastoma cells in culture were evaluated as a way to control tumor progression. The results showed that inhibition of growth and/or induction of apoptosis can be achieved by these molecules in human glioblastoma cells. Inhibition of DNA synthesis precedes induction of apoptosis and growth inhibition. The substituents at C-1, C-2, C-3,C-4, and C-6 on the pyranosidic scaffold are important to modulate the action and the efficacy of these molecules. Human fibroblasts and brain-derived endothelial cells were less sensitive to glycomers than tumor cells. Thus, functionalized aryl beta-D-glycopyranosides represent a new class of molecules potentially able to control the progression of brain tumors.

Chemical Synthesis of beta-Homonojirimycin, of Its N-Butyl Derivative, and of "Methyl Homoazacellobioside"

beta-Homonojirimycin (2) was prepared by the highly stereoselective double reductive amination of a 2,6-heptodiulose derivative (6 or 13) using ammonium formate and NaBH(3)CN. The process was unsuccessful with primary amines. The synthesis of N-butyl-beta-homonojirimycin (19) was achieved by the N-butanoylation of a derivative of 2 followed by the reduction of the resulting tertiary amide. Compound 19 was found to be completely devoid of anti-HIV activity, in marked contrast with N-butyl-1-deoxynojirimycin. The coupling of the 1-O-p-toluenesulfonyl derivative of 2, compound 20, with methyl 2,3,6-tri-O-benzyl-alpha-D-glucopyranoside, followed by a deprotection step, provided pseudodisaccharide 23, the "homoaza" analog of methyl alpha-cellobioside and a potential inhibitor of beta-glucan-processing enzymes.

Toward Overcoming Staphylococcus aureus Aminoglycoside Resistance Mechanisms with a Functionally Designed Neomycin Analogue.

Deoxygenation of the diol groups in rings A and D of neomycin in combination with the introduction of an N1-(l)-HABA group in the 2-deoxystreptamine subunit (ring B) leads to a novel and potent antibiotic (1) with activity against strains of S. aureus carrying known aminoglycoside resistance determinants, as well as against an extended panel of Methicillin-resistant S. aureus isolates (n = 50). Antibiotic 1 displayed >64 fold improvement in MIC50 and MIC90 against this MRSA collection when compared to the clinically relevant aminoglycosides amikacin and gentamicin. The synthesis was achieved in six steps and 15% overall yield.