Synthesis of N-propargylphenelzine and analogues as neuroprotective agents

Synthesis of trisubstituted hydrazine via MnO2-promoted oxidative coupling of N,N-disubstituted hydrazine and boronic ester

A MnO2-promoted oxidative coupling process between N,N-disubstituted hydrazine and boronic ester is reported. A 1,1-diazene species is firstly generated upon oxidation of a hydrazine substrate in the presence of MnO2 which then interacts with boronic ester to form the key intermediate boron-ate complex, followed by migration from boron to nitrogen to form a new C-N bond. This new finding provides mild, scalable, and operationally straightforward access to trisubstituted hydrazine.

An update on amine oxidase inhibitors: multifaceted drugs

Although not used as extensively as other antidepressants for the treatment of depression, the monoamine oxidase (MAO) inhibitors continue to hold a niche in psychiatry and to have a relatively broad spectrum with regard to treatment of psychiatric and neurological disorders. Experimental and clinical research on MAO inhibitors has been expanding in the past few years, primarily because of exciting findings indicating that these drugs have neuroprotective properties (often independently of their ability to inhibit MAO). The non-selective and irreversible MAO inhibitors tranylcypromine (TCP) and phenelzine (PLZ) have demonstrated neuroprotective properties in numerous studies targeting elements of apoptotic cascades and neurogenesis. l-Deprenyl and rasagiline, both selective MAO-B inhibitors, are used in the management of Parkinson's disease, but these drugs may be useful in the treatment of other neurodegenerative disorders given that they demonstrate neuroprotective/neurorescue properties in a wide variety of models in vitro and in vivo. Although the focus of studies on the involvement of MAO inhibitors in neuroprotection has been on MAO-B inhibitors, there is a growing body of evidence demonstrating that MAO-A inhibitors may also have neuroprotective properties. In addition to MAO inhibition, PLZ also inhibits primary amine oxidase (PrAO), an enzyme implicated in the etiology of Alzheimer's disease, diabetes and cardiovascular disease. These multifaceted aspects of amine oxidase inhibitors and some of their metabolites are reviewed herein.

2-Phenyl-N'-(2-phenyl-acet-yl)acetohydrazide

In the title compound, C₁₆H₁₆N₂O₂, the N′-acetyl­acetohydrazide group is approximately planar (r.m.s. deviation = 0.018 Å for the eight non-H atoms) and makes dihedral angles of 81.92 (6) and 65.19 (6)° with the terminal phenyl rings. The phenyl rings form a dihedral angle of 62.60 (7)°. In the crystal, mol­ecules are linked into sheets lying parallel to (001) by N—H⋯O and C—H⋯O hydrogen bonds. One O atom accepts one N—H⋯O and one C—H⋯O hydrogen bond and the other O atom accepts one N—H⋯O and two C—H⋯O hydrogen bonds. The N—H⋯O hydrogen bonds lead to R₂²(8) loops and the C—H⋯O hydrogen bonds generate R₂¹(6) loops.

Aldehyde load in ischemia-reperfusion brain injury: neuroprotection by neutralization of reactive aldehydes with phenelzine

In ongoing studies of the neuroprotective properties of monoamine oxidase inhibitors, we found that phenelzine provided robust neuroprotection in the gerbil model of transient forebrain ischemia, with drug administration delayed up to 3 h post reperfusion. Since ischemia-reperfusion brain injury is associated with large increases in the concentrations of reactive aldehydes in the penumbra area, we investigated if the hydrazine function of phenelzine was capable of sequestering reactive aldehydes. Both aminoaldehydes and acrolein are generated from the metabolism of polyamines to putrescine by polyamine oxidase. These toxic aldehydes in turn compromise mitochondrial and lysosomal integrity and initiate apoptosis and necrosis. Previous studies have demonstrated that pharmacological neutralization of reactive aldehydes via the formation of thioacetal derivatives results in significant neuroprotection in ischemia-reperfusion injury, in both focal and global ischemia models. In our studies of acrolein and 3-aminopropanal toxicity, using an immortalized retinal cell line, we found that aldehyde sequestration with phenelzine was neuroprotective. The neuroprotection observed with phenelzine is in agreement with previous studies of aldehyde sequestering agents in the treatment of ischemia-reperfusion brain injury and supports the concept that "aldehyde load" is a major factor in the delayed cell losses of the ischemic penumbra.

Facile Synthesis of Mono-, Di-, and Trisubstituted Alpha-Unbranched Hydrazines

Methods for the alkylation of di-tert-butyl hydrazine-1,2-dicarboxylate were investigated. It was found that under mild conditions mono- or di-substituted hydrazine derivatives were obtained in good to excellent yield. Furthermore, it was shown that one of the two Boc-groups of the disubstituted derivatives was selectively removed by heating, leading to precursors for trisubstituted hydrazines.

New Synthesis of Propargylic Amines from 2-(Bromomethyl)aziridines. Intermediacy of 3-Bromoazetidinium Salts

A new, efficient, and straightforward synthesis provides propargylamines in high overall yields (64-77%) by transformation of 1-(arylmethyl)-2-(bromomethyl)aziridines into N,N-di(arylmethyl)-N-(2-propynyl)amines via N-(2,3-dibromopropyl)amines and N-(2-bromo-2-propenyl)amines. The conversion of N-(2,3-dibromopropyl)amines into N-(2-bromo-2-propenyl)amines is based on a novel analogue of the Hofmann elimination. A Yamaguchi-Hirao alkylation, a Sonogashira coupling, or a hydroarylation reaction further functionalized these propargylamines toward potentially interesting compounds for medicinal and agrochemical use.