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A series of novel 2-pyridyl, 4-morpholinyl substituted thiazolo[5,4-b]pyridine analogues have been designed and synthesized in this paper. These thiazolo[5,4-b]pyridines were efficiently prepared in seven steps from commercially available substances in moderate to good yields. All of these N-heterocyclic compounds were characterized by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) analysis and tested for phosphoinositide 3-kinase (PI3K) enzymatic assay. The results indicated that these N-heterocyclic compounds showed potent PI3K inhibitory activity, and the IC50 of a representative compound (19a) could reach to 3.6 nm. The structure−activity relationships (SAR) study showed that sulfonamide functionality was important for PI3Kα inhibitory activity, and 2-chloro-4-florophenyl sulfonamide (19b), or 5-chlorothiophene-2-sulfonamide (19c) showed potent inhibitory activity with a nanomolar IC50 value. The pyridyl attached to thiazolo[5,4-b]pyridine was another key structural unit for PI3Kα inhibitory potency, and replacement by phenyl lead to a significant decrease in activity. Enzymatic Inhibition results showed that compound 19a inhibited PI3Kα, PI3Kγ, or PI3Kδ with a nanomolar IC50 value, but its inhibitory activity on PI3Kβ was approximately 10-fold reduced. Further docking analysis revealed that the N-heterocyclic core of compound 19a was directly involved in the binding to the kinase through the key hydrogen bonds interaction.

Nicotinamide adenine dinucleotide (NAD), one of the most important coenzymes in the cells, is a substrate of the signaling enzyme CD38, by which NAD is converted to a second messenger, cyclic ADP-ribose, which releases calcium from intracellular calcium stores. Starting with 2′-deoxy-2′-fluoroarabinosyl-β-nicotinamide adenine dinucleotide (ara-F NAD), a series of NAD analogues were synthesized and their activities to inhibit CD38 NAD glycohydrolase (NADase) were evaluated. The adenosine-modified analogues showed potent inhibitory activities, among which 2′-deoxy-2′-fluoroarabinosyl-β-nicotinamide guanine dinucleotide (ara-F NGD) was the most effective one. The structure-activity relationship of NAD analogues was also discussed.

A novel trifluoromethylated analogue of cADPR, 8-CF3-cIDPDE (5) was designed and synthesized via construction of N1,N9-disubstituted hypoxanthine, trifluoromethylation and intramolecular condensation. A series of acyclic analogues of cADPR were also designed and synthesized. These compounds could be useful molecules for studying the structure-activity relationship of cADPR analogues and exploring the cADPR/RyR Ca2+ signalling system.

A novel trifluoromethylated analogue of cADPR, 8-CF3-cIDPDE (5) was designed and synthesized via construction of N¹,N9-disubstituted hypoxanthine, trifluoromethylation and intramolecular condensation. A series of acyclic analogues of cADPR were also designed and synthesized. These compounds could be useful molecules for studying the structure-activity relationship of cADPR analogues and exploring the cADPR/RyR Ca2+ signalling system. [ABSTRACT FROM AUTHOR]