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Ribonuclosides derived from 6‐hetaryl‐7‐dezapurines are potent cytostatics, but their mechanism of action is unknown. Here we designed and synthesized a series of cyclic and acyclic nucleoside phosphonates, as well as carboxy, cyano, sulfo, and sulfonamide acyclic analogues derived from 6‐thiophen‐2‐yl‐7‐deazapurine and 7‐fluoro‐6‐thiophen‐2‐yl‐7‐deazapurine as ribonucleoside monophosphate mimics. None of these analogues exerted significant cytotoxic and antiviral activity. [ABSTRACT FROM AUTHOR]

Suitably protected (R)‐ and (S)‐HPEP {9‐[3‐hydroxy‐2‐(phosphonoethoxy)propyl]} derivatives containing adenine and thymine nucleobases were prepared as monomers for the introduction of acyclic nucleotide units into oligonucleotides. The solid phase synthesis of a series of ribo and 2′‐deoxyribo nonamers containing (R)‐HPEP and (S)‐HPEP units was successfully performed in both 5′ → 3′ and 3′ → 5′ directions. The measurement of thermal characteristics of the complexes of modified nonamers with complementary DNA and RNA strands revealed a general destabilizing effect of the introduced acyclic units on the thermal stability, but in several cases [modif.RNA*RNA and modif.DNA*RNA with (S)‐HPEPA units], the duplexes were characterized in terms of Tm values. A solid‐phase synthesis afforded a series of ribo and 2′‐deoxyribo nonamers containing acyclic nucleotide units. A general destabilizing effect of the introduced acyclic units on the thermal stability of complexes of modified nonamers with the complementary DNA and RNA strands was observed, but in cases with (S)‐HPEPA units, the duplexes were characterized in terms of Tm values. [ABSTRACT FROM AUTHOR]

• New acyclic nucleotide analogs with 1,2,4-thiadiazole base were synthesized. • 5-Amino-1,2,4-thiadiazol-3(2 H)-one derivatives inhibit Cathepsin K and GSK-3β. • 1,2,4-Thiadiazol-3(2 H)-one ring is stabilized by substitution at the 5-amino group. In analogy to antiviral acyclic nucleoside phosphonates, a series of 5-amino-3-oxo-1,2,4-thiadiazol-3(2 H)-ones bearing a 2-phosphonomethoxyethyl (PME) or 3-hydroxy-2-(phosphonomethoxy)propyl (HPMP) group at the position 2 of the heterocyclic moiety has been synthesized. Diisopropyl esters of PME- and HPMP-amines have been converted to the N -substituted ureas and then reacted with benzoyl, ethoxycarbonyl, and Fmoc isothiocyanates to give the corresponding thiobiurets, which were oxidatively cyclized to diisopropyl esters of 5-amino-3-oxo-2-PME- or 2-HPMP- 1,2,4-thiadiazol-3(2 H)-ones. The phosphonate ester groups were cleaved with bromotrimethylsilane, yielding N 5-protected phosphonic acids. The subsequent attempts to remove the protecting group from N 5 under alkaline conditions resulted in the cleavage of the 1,2,4-thiadiazole ring. Similarly, compounds with a previously unprotected 5-amino-1,2,4-thiadiazolone base moiety were stable only in the form of phosphonate esters. The series of twenty-one newly prepared 1,2,4-thiadiazol-3(2 H)-ones were explored as potential inhibitors of cysteine-dependent enzymes – human cathepsin K (CatK) and glycogen synthase kinase 3β (GSK-3β). Several compounds exhibited an inhibitory activity toward both enzymes in the low micromolar range. The inhibitory potency of some of them toward GSK-3β was similar to that of the thiadiazole GSK-3β inhibitor tideglusib, whereas others exhibited more favorable toxicity profile while retaining good inhibitory activity. [ABSTRACT FROM AUTHOR]