Dual antagonists of platelet activating factor and histamine. 3. Synthesis, biological activity and conformational implications of substituted N-acyl-bis-arylcycloheptapiperazines

Low-temperature 1H and 13C NMR spectra of N-substituted 1,2,3,4-tetrahydropyrazino[1,2-a]indoles

The temperature-dependent (1)H and (13)C NMR spectra of 2-(2-butynyl)-10-methyl-1,2,3,4-tetrahydropyrazino[1,2-a]indole (4) (as a representative example of 1-9) in CFCl(3) + CD(2)Cl(2) solution are described and discussed. Below 183 K, the hexahydropyrazine ring inversions become slow on the NMR time-scale and 4 exists in principle as two conformational diastereomers. In fact, only one was observed with the N-2 substituent in an equatorial position as shown by a low-temperature NOESY experiment. The energy barrier for conformational interchange was calculated from NMR data to be 8.3 kcal mol(-1) (1 kcal = 4.184 kJ), in agreement with quantum chemical calculations. Unambiguous assignments for all proton and carbon resonances of 1-9 were made using 1D (APT, DEPT, NOE difference) and 2D (COSY, NOESY, gHMQC, gHMBC) NMR techniques.

Structure–activity relationship studies on unifiram (DM232) and sunifiram (DM235), two novel and potent cognition enhancing drugs

Structure-activity relationships on two novel potent cognition enhancing drugs, unifiram (DM232, 1) and sunifiram (DM235, 2), are reported. Although none of the compounds synthesised reached the potency of the parent drugs, some fairly active compounds have been identified that may represent new leads to develop other cognition enhancing drugs. An interesting result of this research is the identification of two compounds (13 and 14) that are endowed with amnesing activity (the opposite of the activity of the original molecules) and are nearly equipotent to scopolamine. Moreover, two compounds of the series (5 and 6) were found endowed with analgesic activity on a rat model of neuropathic pain at the dose of 1 mg/kg.

Conformational considerations in the design of dual antagonists of platelet-activating factor (PAF) and histamine

Following the discovery of the first dual antagonist of platelet-activating factor (PAF) and histamine, 1-acetyl-4-(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2-b]pyridin- 11-ylidene)piperidine, Sch 37370, 1, a related series of structures, exemplified by (+/-)-1-acetyl-4-(8-chloro-5,6-dihydro-11H-benzo[5,6]-cyclohepta[1,2-b] pyridin-11-yl)piperazine, Sch 40338, 2, were prepared. Interestingly, the compounds exhibited a parallel structure antiallergy activity relationship, suggesting that the two series may adopt a common conformation at the PAF receptor. Conformational analysis led to a proposal for this bioactive conformation accessible to both series. The synthesis of novel conformationally constrained analogues that might mimic the proposed bioactive conformation of these compounds, and the evaluation of their in vitro antiallergy activity form the subject matter of this report.