Structure-Affinity Relationships and Structure-Kinetic Relationships of 1,2-Diarylimidazol-4-carboxamide Derivatives as Human Cannabinoid 1 Receptor Antagonists.

We report on the synthesis and biological evaluation of a series of 1,2-diarylimidazol-4-carboxamide derivatives developed as CB1 receptor antagonists. These were evaluated in a radioligand displacement binding assay, a [35S]GTPγS binding assay, and in a competition association assay that enables the relatively fast kinetic screening of multiple compounds. The compounds show high affinities and a diverse range of kinetic profiles at the CB1 receptor and their structure-kinetic relationships (SKRs) were established. Using the recently resolved hCB1 receptor crystal structures, we also performed a modeling study that sheds light on the crucial interactions for both the affinity and dissociation kinetics of this family of ligands. We provide evidence that, next to affinity, additional knowledge of binding kinetics is useful for selecting new hCB1 receptor antagonists in the early phases of drug discovery.

Synthesis, screening and docking of small heterocycles as glycogen phosphorylase inhibitors.

A series of morpholine substituted amino acids (phenylalanine, leucine, lysine and glutamic acid) was synthesized. A fragment-based screening approach was then used to evaluate a series of small heterocycles, including morpholine, oxazoline, dihydro-1,3-oxazine, tetrahydro-1,3-oxazepine, thiazoline, tetrahydro-1,3-pyrimidine, tetrahydro-1,3-diazepine and hexahydro-1H-benzimidazole, as potential inhibitors of Glycogen Phosphorylase a. Thiazoline 7 displayed an improved potency (IC50 of 25 µM) and had good LE and LELP values, as compared to heterocycles 1, 5, 9-13 and 19 (IC50 values of 1.1 mM-23.9 mM). A docking study using the crystal structure of human liver Glycogen Phosphorylase, provided insight into the interactions of heterocycles 5, 7, 9-13 and 19 with Glycogen Phosphorylase.

Cyclodehydration of N-(aminoalkyl)benzamides under mild conditions with a Hendrickson reagent analogue.

Methods for the cyclodehydration of N-(aminoalkyl)benzamides are few and employ harsh reaction conditions. We have found that the easily prepared phosphonium anhydrides 1 (Hendrickson reagent) or 2 can be used for cyclodehydration of N-(aminoalkyl)benzamides under very mild conditions (room temperature) to produce five-, six-, and seven-membered cyclic amidines. Good yields are obtained by employing a temporary trityl group protection strategy. Cyclic analogue 2 can be used when the product cyclic amidine is organic-soluble, thus producing water-soluble byproducts.

The use of phosphonium anhydrides for the synthesis of 2-oxazolines, 2-thiazolines and 2-dihydrooxazine under mild conditions.

Beta-hydroxy amides 6 and 7 were treated with triphenylphosphonium anhydride trifluoromethane sulfonate (3), or the cyclic analogue 4, to generate 2-oxazolines 5 and 8 under mild conditions. The reaction was optimised by examining the number of equivalents of reagents 3 or 4, or diisopropylethyl amine required to best effect cyclisation. The effects of altering the reaction temperature, reaction time, concentration, solvent, and addition rate also were investigated. However, it was found that use of a trityl group to block reaction at the hydroxyl or thiol group of the starting amides, and subsequent in situ detritylation, in the absence of base, led to greatly improved yields. Reagent 4 offered significant advantages in the purification of products and was used to dehydrate a range of trityl derivatives to form simple oxazolines, thiazolines, and a dihydro-1,3-oxazine, in high yield (85-99%), as well as a tetrahydro-1,3-oxazepine (31%).

Selective mono reduction of bis-phosphine oxides under mild conditions.

Bis-phosphine oxides can be selectively reduced to bis-phosphine monoxides under exceptionally mild conditions using triflic anhydride and a thiol.

Evaluation of novel hyphodermin derivatives as glycogen phosphorylase a inhibitors.

The lipophilicity, permeability, solubility, polar surface area and 'rule-of-five' properties were assessed, using QikProp v2.5 (Schrödinger, Inc.) and ALOGPS 2.1 calculations, for 25 Hyphodermin derivatives. These compounds obeyed the 'rule-of-five', and the calculated physicochemical values were generally within desired limits. All compounds were tested against Glycogen Phosphorylase a (GPa). Four phenyl and benzyl substituted 2-oxo-hexahydro and tetrahydrobenzo[cd]indole carboxylic acids were identified as novel inhibitors of GPa with estimated IC(50) values in the range 0.8-1.3mM. Molecular modelling of these novel inhibitors was used to obtain the main structural features of this class of molecule for future structure-activity relationship studies.

The structure of polymer-supported triphenylphosphine ditriflate: a potentially useful reagent in organic synthesis.

The structure of a polymer-supported version of the Hendrickson "POP" reagent, prepared by the reaction of polymer-supported triphenylphosphine oxide 1 with triflic anhydride, is established as an equilibrium mixture of polymer-supported triphenylphosphine ditriflate 3 (delta 79.4 ppm) and polymer-supported phosphonium anhydride 4 (delta 73.3 ppm). The (31)P NMR chemical shift reported previously for 3 is shown to be incorrect.