6‐Substituted Purines as Inhibitors of 15‐Lipoxygenase; a Structure‐Activity Study

Abstract

15-lipoxygenase (15-LO) has been implicated in oxidation of low-density lipoproteins (LDL), a process believed to be important for the development of atherosclerosis, as well as other pathogenic conditions. Potent and selective inhibitors of 15-LO may have a drug potential. In this study, purines with a variety of substituents have been examined as inhibitors of 15-lipoxygenase (15-LO) from soybeans. Several 6-substitued purines where the purine ring and a phenyl ring in the substituent were separated by a "spacer" were synthesized and their ability to inhibit the enzyme was explored. Sepa ration of the purine and the phenyl rings with none, one or two sp3-carbons resulted in essentially inactive compounds, trans-styrylpurines and phenylethynylpurines, on the other hand, they exhibited activity close to the well-known 15-LO inhibitor quercetin. High activity was also found when the "spacer" was a trans-cyclopropyl ring. The shape of the spacer was important; a corresponding cis-cyclopropylpurine exhibited much less affinity for the enzyme. Only minor differences in inhibitory activity against 15-LO were found regardless of whether an N-substituent was situated on N-9 or N-7, even when the N-substituent was relatively large. Also, a variety of substituents in the purine 2- and 8-position were well tolerated.

Synthetic Studies Directed towards Agelasine Analogs – Synthesis, Tautomerism, and Alkylation of 2‐Substituted N‐Methoxy‐9‐methyl‐9H‐purin‐6‐amines

“…We have also previously observed demethylation of certain other methoxypurines. [13] Ethoxypurine 2g, on the other hand, gave the corresponding benzylated products (3g and 4g) without any detectable cleavage of the alkoxy group. All compounds 3 existed solely as imino tautomers in [D 6 ]DMSO according to NMR, as previously reported for compound 3a [2b] and related structures.…”

“…[3] We observed great variations in the 2:2Ј ratio in solution among compounds 2a-2i ( Table 2). The tautomers were identified mainly from their 13 C NMR and 15 N NMR shift values. In amino tautomers 2, the resonance from C-4 appeared at ca.…”

“…The decoupled 13 C NMR spectra were recorded at 150 MHz or 75 MHz with the instruments mentioned above. 15 N NMR shifts, reported relative to liquid ammonia (δ = 0 ppm) according to literature guidelines, [15] were taken from gs-[ 1 H, 15 N] HSQC and gs-[ 1 H, 15 N] HMBC spectra recorded at 60 MHz with the Bruker AVII600 instrument or at 50 MHz with the Bruker Avance DRX 500 instrument with Me 15 NO 2 as an external standard.…”

“…1 H NMR (300 MHz, CD 3 OD): δ = 9.27 (s, 1 H, H-8), 2.81 (s, 3 H, CH 3 ) ppm. 13 + , 133 (100), 121 (37), 120 (50). HRMS (EI): calcd.…”

Development of a Fluorescent Intensity Assay Amenable for High-Throughput Screening for Determining 15-Lipoxygenase Activity

“…21 The importance of 15-LO-1 in several diseases has provoked numerous attempts to identify specific inhibitors, including screening of chemical compound libraries, virtual screening, and identification of natural products. [21][22][23][24][25][26][27][28][29][30][31][32] Especially interesting was the discovery of potent and cell-active 15-LO inhibitors that recently was described by Bristol-Myer-Squibb. 27 As part of our ongoing studies of the human 15-LO-1 enzyme, we have developed an enzyme-and a cell-based assay amenable for high-throughput screening (HTS).…”