Abstract-Apelin peptides mediate beneficial effects on the cardiovascular system and are being targeted as potential new drugs. However, apelin peptides have extremely short biological half-lives, and improved understanding of apelin peptide metabolism may lead to the discovery of biologically stable analogues with therapeutic potential. We examined the ability of angiotensin-converting enzyme 2 (ACE2) to cleave and inactivate pyr-apelin 13 and apelin 17, the dominant apelin peptides. Computer-assisted modeling shows a conserved binding of pyr-apelin 13 and apelin 17 to the ACE2 catalytic site. In ACE2 knockout mice, hypotensive action of pyr-apelin 13 and apelin 17 was potentiated, with a corresponding greater elevation in plasma apelin levels. Similarly, pharmacological inhibition of ACE2 potentiated the vasodepressor action of apelin peptides. Biochemical analysis confirmed that recombinant human ACE2 can cleave pyr-apelin 13 and apelin 17 efficiently, and apelin peptides are degraded slower in ACE2-deficient plasma. The biological relevance of ACE2-mediated proteolytic processing of apelin peptides was further supported by the reduced potency of pyr-apelin 12 and apelin 16 on the activation of signaling pathways and nitric oxide production from endothelial cells. Importantly, although pyr-apelin 13 and apelin 17 rescued contractile function in a myocardial ischemia-reperfusion model, ACE2 cleavage products, pyr-apelin 12 and 16, were devoid of these cardioprotective effects. We designed and synthesized active apelin analogues that were resistant to ACE2-mediated degradation, thereby confirming that stable apelin analogues can be designed as potential drugs. We conclude that ACE2 represents a major negative regulator of apelin action in the vasculature and heart. residue and the enzymatic processes involved in its removal from the native apelin peptide remains poorly defined. Using loss-of-function and gain-of-function strategies, we here define a critical role of angiotensin-converting enzyme 2 (ACE2) in the proteolytic cleavage of the C-terminal phenylalanine residue in pyr-apelin 13 and apelin 17. Importantly, this degradative site can be modified to produce relatively stable apelin analogues as potential therapeutic agents. Methods In Silico Modeling of Apelin Peptide Binding to ACE2We selected the structure of human apo-ACE2 (PDB ID: 1R42) mainly because of its high resolution, appropriate R-factor, and errorless electron density map. 16 This structure was equilibrated in constant pressure-temperature condition (NVT, NPT) in the Groningen Machine for Chemical Simulations (GROMACS). 17 We performed knowledgebased docking using our understanding from ACE-substrate bound complex structure. For this purpose, we have used the Angiotensin II (Ang II)-bound ACE complex (PDB ID: 4APH) 18 and MLN-4760 inhibitor bound ACE2 complex (PDB ID: 1R4L). 16,[18][19][20] We modeled the ACE2-Ang II, ACE2-pyr-apelin 13, and ACE2-apelin 17 complexes using these 2 above mentioned reference structures as a template. We built th...

The carbon–carbon (C–C) bond cleavage of cyclopropanols is a wide area of research with much current activity. This review highlights new developments in this area over the past two decades. A summary is made of the three main reactivity modes, namely, homoenolate chemistry, β-keto radical chemistry, and acid-catalyzed ring-opening, as well as all other methods for the C–C bond cleavage and functionalization of cyclopropanols, including base-mediated ring-opening, metal-catalyzed C–C insertions and eliminations, oxidative fragmentation using hypervalent iodine reagents, reactions of donor–acceptor cyclopropanols, and pericylic reactions. Emphasis is placed on the synthetic utility of cyclopropanols and related derivatives, which have emerged as unique three-carbon synthons.

Apelin is an important mammalian peptide hormone with a range of physiological roles, especially in the cardiovascular system. The apelinergic system is a promising target for treatment of disease, but this remains to be realized due to rapid proteolysis of apelin-derived peptides by proteases, including neprilysin (NEP). The synthetic analogues modified within the NEP degradation site ("RPRL" motif) showed improved in vitro proteolytic stability while maintaining receptor-binding affinities, with three candidate peptides retaining full cardiovascular activities for potential therapeutic application. Many such analogues proved physiologically inactive even with relatively conservative modifications, highlighting the importance of this region for full agonist activity of this peptide hormone.

There is an increasing interest in cyclobutanes within the medicinal chemistry community. Therefore, methods to prepare cyclobutanes that contain synthetic handles for further elaboration are of interest. Herein, we report...

Cyclopropylamines are prevalent motifs in pharmaceuticals and agrochemicals. Herein, we report the synthesis of trans-2-substituted-cyclopropylamines in high diastereoselectivity from readily available α-chloroaldehydes. The reaction proceeds via trapping of an electrophilic zinc homoenolate with an amine followed by ring-closure to generate the cyclopropylamine product. We have also observed that cis/trans-isomerization of the cyclopropylamine can occur in the presence of zinc halide salts and that this process can be turned off by the addition of a polar aprotic co-solvent to the reaction. File list (2) download file view on ChemRxiv Rousseaux-Cyclopropylamines-Manuscript ChemRxiv... (392.68 KiB) download file view on ChemRxiv Rousseaux-Cyclopropylamines-SI ChemRxiv.pdf (3.16 MiB)