Design, synthesis, and evaluation of novel 2-substituted-4-aryl-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,5]oxazocin-5-ones as NK1 antagonists

Facile assembly of 1,5-diazocan-2-ones via cyclization of tethered sulfonamides to cyclopropenes

The sulfonamide moiety was evaluated as an activating and stabilizing functional group in the metal-templated strain release-driven intramolecular nucleophilic addition of amines to cyclopropenes to generate 1,5-diazocan-2-ones.

Unravelling the binding mechanism and protein stability of human serum albumin while interacting with nefopam analogues: a biophysical and insilico approach

In this study, molecular binding affinity was investigated for Nefopam analogues (NFs), a functionalized benzoxazocine, with human serum albumin (HSA), a major transport protein in the blood. Its binding affinity and concomitant changes in its conformation, binding site and simulations were also studied. Fluorescence data revealed that the fluorescence quenching of HSA upon binding of NFs analogues is based on a static mechanism. The three analogues of NFs binding constants (K_A) are in the order of NF3 > NF2 > NF1 with values of 1.53 ± .057 × 10⁴, 2.16 ± .071 × 10⁴ and 3.6 ± .102 × 10⁵ M^-1, respectively. Concurrently, thermodynamic parameters indicate that the binding process was spontaneous, and the complexes were stabilized mostly by hydrophobic interactions, except for NF2 has one hydrogen bond stabilizes it along with hydrophobic interactions. Circular dichroism (CD) studies revealed that there is a decrease in α-helix with an increase in β-sheets and random coils signifying partial unfolding of the protein upon binding of NFs, which might be due to the formation of NFs-HSA complexes. Further, molecular docking studies showed that NF1, NF2 and NF3 bound to subdomains IIIA, IB and IIA through hydrophobic interactions. However, NF1 have additionally formed a single hydrogen bond with LYS 413. Furthermore, molecular simulations unveiled that NFs binding was in support with the structural perturbation observed in CD, which is evident from the root mean square deviation and R_g fluctuations. We hope our insights will provide ample scope for engineering new drugs based on the resemblances with NFs for enhanced efficacy with HSA.

Synthesis and X-ray structural studies of a substituted 2,3,4,5-tetrahydro-1H-3-benzazonine and a 1,2,3,5-tetrahydro-4,3-benzoxazonine

Using a common 1-(1-phenylethenyl)-1,2,3,4-tetrahydroisoquinoline precursor to the required ylide or N-oxide intermediate, the Stevens [2,3] and analogous Meisenheimer [2,3] sigmatropic rearrangements have been applied to afford concise syntheses of phenyl -substituted representatives of each of the reduced 1H-3-benzazonine and 4,3-benzoxazonine systems, respectively. Single crystal X-ray structure determinations were employed to define the conformational characteristics for each ring type.

Annulation of Eight- to Ten-Membered Oxaza Rings to the Benzo[b]thiophene System by Intramolecular Nucleophilic Displacement

Concise synthetic routes to 2H-benzo[b]thieno[3,2-b][1,5]oxazocin-6(3H)-one, and the new benzo[b]thieno[3,2-b][1,5]oxazonin-7(2H)-one and 2H-benzo[b]thieno[3,2-b][1,5]oxazecin-8(3H)-one systems, have been developed based on intramolecular nucleophilic displacement in the key ring forming step.

One pot synthesis of cis-bispyrimidodiazepinone derivatives via low-valent titanium reagent (TiCl4/Sm)

An efficient and convenient method for the preparation of cis-bispyrimidodiazepinone derivatives has been described. A variety of substrates can participate in the process with good yields, making this methodology suitable for library synthesis in drug discovery efforts. The mechanistic course of the reaction suggests the involvement of reduction, coupling which determine the products' configuration and cyclization by one-pot.

Synthesis of novel 8,9-dihydro-5H-pyrimido[4,5-e][1,4]diazepin-7(6H)-ones

Practical and efficient methods have been developed for the synthesis of 4,6,8,9-tetrasubstituted 8,9-dihydro-5H-pyrimido[4,5-e][1,4]diazepin-7(6H)-ones from 4,6-dicholoropyrimidine aldehyde, N-substituted amino acid esters, and amines in five steps. This synthetic strategy is based on suitably substituted pyrimidines as bis-electrophilic species reacting with various amines to construct the pyrimido[4,5-e][1,4]diazepine core with a strategically anchored functional group for further derivatization. The utility of this methodology was demonstrated through the preparation of a 33-membered library of representative 8,9-dihydro-5H-pyrimido[4,5-e][1,4]diazepin-7(6H)-ones in good to excellent yields.

A facile synthesis of pyrrolo-(di)-benzazocinones via an intramolecular N-acyliminium ion cyclisation

A facile, moderate to high yielding synthesis of hexahydro-(di)-benzazocinones is described via an intramolecular N-acyliminium ion cyclisation. The iminium ion intermediates are formed from the readily available 4,4-diethoxybutyl amides with an excess of triflic acid. For electron-withdrawing substituents, better yields were obtained from the pre-formed 2-hydroxypyrrolidine amides. From NMR studies, at ambient temperatures the pyrrolo-benzazocin-3-ones exist as a slowly equilibrating mixture of two conformations.

AMTB, a TRPM8 channel blocker: evidence in rats for activity in overactive bladder and painful bladder syndrome

The activation of the TRPM8 channel, a member of the large class of TRP ion channels, has been reported to be involved in overactive bladder and painful bladder syndrome, although an endogenous activator has not been identified. In this study, N-(3-aminopropyl)-2-{[(3-methylphenyl) methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride salt (AMTB) was evaluated as a TRPM8 channel blocker and used as a tool to evaluate the effects of this class of ion channel blocker on volume-induced bladder contraction and nociceptive reflex responses to noxious bladder distension in the rat. AMTB inhibits icilin-induced TRPM8 channel activation as measured in a Ca(2+) influx assay, with a pIC(50) of 6.23. In the anesthetized rat, intravenous administration of AMTB (3 mg/kg) decreased the frequency of volume-induced bladder contractions, without reducing the amplitude of contraction. The nociceptive response was measured by analyzing both visceromotor reflex (VMR) and cardiovascular (pressor) responses to urinary bladder distension (UBD) under 1% isoflurane. AMTB (10 mg/kg) significantly attenuated reflex responses to noxious UBD to 5.42 and 56.51% of the maximal VMR response and pressor response, respectively. The ID50 value on VMR response was 2.42 +/- 0.46 mg/kg. These results demonstrate that TRPM8 channel blocker can act on the bladder afferent pathway to attenuate the bladder micturition reflex and nociceptive reflex responses in the rat. Targeting TRPM8 channel may provide a new therapeutic opportunity for overactive bladder and painful bladder syndrome.

Natural compounds: leads or ideas? Bioinspired molecules for drug discovery

In this article, we compare drugs of natural origin to synthetic compounds and analyze the reasons why natural compounds occupy a place of choice in the current pharmacopoeia. The observations reported here support the design of synthetic compounds inspired from plant alkaloids and their biosynthetic pathway. Our reasoning leads to very efficient syntheses of compounds which complexity matches that of indolomonoterpenic alkaloids.

Process development and large-scale synthesis of NK1 antagonist

A scaleable synthetic route is described to obtain 2-(4-acetylpiperadin-1-yl)-6-[3,5-bis(trifluoromethyl)phenylmethyl]-4-(2-methylphenyl)-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,5]oxazocin-5-one (1, KRP-103) as a neurokinin (NK)(1) antagonist. The key step in the synthesis is the intramolecular cyclization of N-[3,5-bis(trifluoromethyl)phenylmethyl]-N-(3-hydroxypropyl)-4-chloro-6-(2-methylphenyl)-2-methylthiopyrimidine-5-carboxamide (15) which was obtained by amide formation between 4-(2-methylphenyl)-2-methylthio-6-oxo-1,6-dihydropyrimidine-5-carboxylic acid (8) and 3-[3,5-bis(trifluoromethyl)phenylmethylamino]-1-propanol (3). Treatment of 15 with 1,8-diazabicyclo[5,4,0]undec-7-ene provided 6-[3,5-bis(trifluoromethyl)phenylmethyl]-4-(2-methylphenyl)-2-methylthio-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,5]oxazocin-5-one (6). This intermediate (6) is transformed into the candidate compound (1) by two steps; oxidation, and substitution reaction of the resultant sulfone (7) with 1-acetylpiperazine. This synthetic method is free of chromatographic purification and is amenable to large scale synthesis.

Analysis of crucial structural requirements of 2-substituted pyrimido[4,5-b][1,5]oxazocines as NK1 receptor antagonist by axially chiral derivatives

This study aimed to identify the crucial structural features of 2-substituted 8-methylpyrimido[4,5-b][1,5]oxazocine derivatives. Axially chiral 8-methylpyrimido[4,5-b][1,5]oxazocines bearing a substituent at the C-2 position were synthesized and evaluated as NK(1) antagonists. The results revealed that (aR, 8S)-stereochemistry and the substituent at the C-2 position are important for NK(1) receptor recognition.