Ravindra B. Upasani

Discovery of subtype-selective NMDA receptor ligands: 4-benzyl-1-piperidinylalkynylpyrroles, pyrazoles and imidazoles as NR1A/2B antagonists.

4-Benzyl-1-[4-(1H-imidazol-4-yl)but-3-ynyl]piperidine (8) has been identified as a potent antagonist of the NR1A/2B subtype of the NMDA receptor. When dosed orally, this compound potentiates the effects of L-DOPA in the 6-hydroxydopamine-lesioned rat, a model of Parkinsons disease.

Structure-activity relationship for a series of 2-substituted 1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indoles: potent subtype-selective inhibitors of N-methyl-D-aspartate (NMDA) receptors.

A series of 2-substituted 1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indoles was synthesized as potential antagonists for the NR1A/2B subtype of N-methyl-D-aspartate (NMDA) receptors. Assayed by electrical recording under steady-state conditions, 7-hydroxy-2-(4-phenylbutyl)- 1,2,3,4-tetrahydropyrido-[3,4-b]indole (30) was the most potent compound in the series having an IC50 value of 50 nM at the NR1A/2B receptors.

In Vitro and In Vivo Activity of 16,17-dehydro-epipregnanolones: 17,20-Bond Torsional Energy Analysis and D-ring Conformation

AbstractPurpose. Certain neuroactive pregnane steroids (also known as “epalons”) are allosteric modulators of the GABAA receptor and have been shown to be potent anticonvulsants, anxiolytics, sedative/hypnotics, and anesthetic agents. The purpose of this study was to calculate the structural consequences of introduction of a double bond in the 16,17-position and to determine if this modification would selectively reduce sedative activity, but maintain the potent anticonvulsant activity of neuroactive steroids. Methods. We have studied the biochemical and behavioral effects of introducing a 16,17 double bond into the naturally occurring neuroactive steroids, 3α-hydroxy-5α-pregnan-20-one (3α,5α-P) and 3α-hydroxy-5β-pregnan-20-one (3α,5β-P) and three synthetic neuroactive steroid derivatives, 3α-hydroxy-3β-methyl-5α-pregnan-20-one (3α,3βMe,5α-P), 3α-hydroxy-5α-androstane (3α,5α-A), and alphaxalone (3α,5α-11-one-P). Results. The 16-ene analogs of most of these neuroactive steroids were found to be 7- and 16-fold less potent in inhibiting [35S]TBPS binding to GABAA receptors and in a similar fashion, had reduced anticonvulsant and sedative potency in proportional amounts. The exception was the androstane (3α,5α-A) without a 17-acetyl group, that had virtually identical IC50 and ED50 values for the saturated and unsaturated derivatives. Calculation of the torsional energy profile for each of the 17-acetyl side chain conformations showed that the conformational energy minima found in the α,β-unsaturated keto systems, produce an orientation of the 20-keto group that is rotated by 165 degrees when compared to the non-conjugated acetyl group (determined by X-ray crystallography and its minimum energy conformation). Conclusions. The modified orientation of the 20-keto group of neuroactive steroids containing a 16-ene, provides an explanation for their decreased biological activity overall, but did not lead to an enhanced protective index.