Synthesis and evaluation of a new series of peptide-based endothelin receptor antagonists

Diabetic retinopathy and endothelin system: microangiopathy versus endothelial dysfunction

In the face of the global epidemic of diabetes, it is critical that we update our knowledge about the pathogenesis of diabetes and the related micro alterations on the vascular network in the body. This may ultimately lead to early diagnosis and novel treatment options for delaying the progression of diabetic complications. Research has recently revealed the pivotal role of endothelin in the pathogenesis of diabetic complications, particularly in the regulation of the capillary flow, which is affected in the course of retinopathy. Although there are several reviews on various approaches to the treatment of diabetes, including normalization of glucose and fat metabolism, no reviews in literature have focused on the endothelin system as a therapeutic target or early indicator of diabetic microangiopathy. In this review, we summarize some of the experimental and clinical evidence suggesting that current therapeutic approaches to diabetes may include the modulation of the blood concentration of compounds of the endothelin system. In addition, we will briefly discuss the beneficial effects produced by the inhibition of the production of high levels of endothelin in vasculopathy, with focus on diabetic retinopathy. The cutting-edge technology currently widely used in opththalmology, such as the OCT angiography, allows us to detect very early retinal morphological changes alongside alterations in choroidal and retinal vascular network. Combination of such changes with highly sensitive measurements of alterations in serum concentrations of endothelin may lead to more efficient early detection and treatment of diabetes and related macro/microvascular complications.

Molecular dynamics study-guided identification of cyclic amine structures as novel hydrophobic tail components of hPPARγ agonists

We previously reported that a α-benzylphenylpropanoic acid-type hPPARγ-selective agonist with a piperidine ring as the hydrophobic tail part (3) exhibited sub-micromolar-order hPPARγ agonistic activity. In order to enhance the activity, we planned to carry out structural development based on information obtained from the X-ray crystal structure of hPPARγ ligand binding domain (LBD) complexed with 3. However, the shape and/or nature of the binding pocket surrounding the piperidine ring of 3 could not be precisely delineated because the structure of the omega loop of the LBD was poorly defined. Therefore, we constructed and inserted a plausible omega loop by means of molecular dynamics simulation. We then used the reconstructed LBD structure to design new mono-, bi- and tricyclic amine-bearing compounds that might be expected to show greater binding affinity for the LBD. Here, we describe synthesis and evaluation of α-benzylphenylpropanoic acid derivatives 8. As expected, most of the newly synthesized compounds exhibited more potent hPPARγ agonistic activity and greater hPPARγ binding affinity than 3. Some of these compounds also showed comparable aqueous solubility to 3.

Alpha,gamma-diamino acids: asymmetric synthesis of new constrained 6-amino-3-azabicyclo[3.2.1]octane-6-carboxylic acids

The synthesis of two new diastereomeric 6-amino-3-azabicyclo[3.2.1]octane-6-carboxylic acids exo- and endo-8,9 is reported using exo- and endo-norbornene amino acids as chiral building blocks. This method provides a fast access to optically pure amino acids 8 and 9 which can be considered both alpha,gamma- and alpha,delta-diamino acids containing sterical constraints and characterized by alpha,alpha-disubstitution.