1. Synthesis and pharmacological investigation of azaphthalazinone human histamine H(1) receptor antagonists
Panayiotis A Procopiou, Christopher Browning, Paul M Gore, Sean M Lynn, Stephen A Richards, Robert J Slack, Steven L Sollis Bioorg Med Chem. 2012 Oct 15;20(20):6097-108. doi: 10.1016/j.bmc.2012.08.032. Epub 2012 Aug 31.
5-Aza, 6-aza, 7-aza and 8-aza-phthalazinone, and 5,8-diazaphthalazinone templates were synthesised by stereoselective routes starting from the appropriate pyridine/pyrazine dicarboxylic acids by activation with CDI, reaction with 4-chlorophenyl acetate ester enolate to give a β-ketoester, which was hydrolysed, and decarboxylated. The resulting ketone was condensed with hydrazine to form the azaphthalazinone core. The azaphthalazinone cores were alkylated with N-Boc-D-prolinol at N-2 by Mitsunobu reaction, de-protected, and then alkylated at the pyrrolidine nitrogen to provide the target H(1) receptor antagonists. All four mono-azaphthalazinone series had higher affinity (pK(i)) for the human H(1) receptor than azelastine, but were not as potent as the parent non-aza phthalazinone. The 5,8-diazaphthalazinone was equipotent with azelastine. The least potent series were the 7-azaphthalazinones, whereas the 5-azaphthalazinones were the most lipophilic. The more hydrophilic series were the 8-aza series. Replacement of the N-methyl substituent on the pyrrolidine with the n-butyl group caused an increase in potency (pA(2)) and a corresponding increase in lipophilicity. Introduction of a β-ether oxygen in the n-butyl analogues (2-methoxyethyl group) decreased the H(1) pA(2) slightly, and increased the selectivity against hERG. The duration of action in vitro was longer in the 6-azaphthalazinone series. The more potent and selective 6-azaphthalazinone core was used to append an H(3) receptor antagonist fragment, and to convert the series into the long acting single-ligand, dual H(1) H(3) receptor antagonist 44. The pharmacological profile of 44 was very similar to our intranasal clinical candidate 1.
2. Replacement of the 3'-CH group by nitrogen in the carbocyclic analogue of thymidine
K M Ng, L E Orgel J Med Chem. 1989 Aug;32(8):1754-7. doi: 10.1021/jm00128a015.
We have prepared (4R)-4-thyminyl-D-prolinol, an analogue of 3'-deoxythymidine in which the sugar has been replaced by D-prolinol. This strongly basic secondary amine has been converted to the corresponding hydroxylamine, an analogue of either thymidine or 2'-deoxyxylofuranosylthymine. We have also synthesized a number of simple derivatives of the amine for testing in vitro activity against herpes simplex 1 (HSV-1), human immunodeficiency virus 1 (HIV-1), and a panel of human tumor cell lines. Among these compounds, the hydroxylamine 12 proved active against the human tumor cell lines of breast, colon, and lung origin, with IC50 values of 0.08, 14.02, and 6.91 microM, respectively.
3. Synthesis and biological evaluation of 4-purinylpyrrolidine nucleosides
M L Peterson, R Vince J Med Chem. 1991 Sep;34(9):2787-97. doi: 10.1021/jm00113a017.
The synthesis of several novel carbocyclic purine nucleosides that incorporate a nitrogen in place of carbon 3 of the cyclopentyl moiety are described. These analogues are all derived from the key stereochemically defined intermediate N-(tert-butoxycarbonyl)-O-[(4-methoxyphenyl)diphenylmethyl]-trans- 4- hydroxy-D-prolinol (19), which was accessible in 61.1% overall yield for a five-step sequence starting from cis-4-hydroxy-D-proline. The heterocyclic bases, 6-chloropurine and 2-amino-6-chloropurine, are efficiently introduced onto the pyrrolidine ring via a Mitsunobu-type coupling procedure with triphenylphosphine and diethyl azodicarboxylate. Standard transformations and removal of protecting groups gave the cis-adenine (26), hypoxanthine (27), 2,6-diaminopurine (28), and guanine (29) D-prolinol derivatives. In addition, a related sequence from trans-4-hydroxy-L-proline provided the enantiomeric L-prolinol guanine derivative (36). Lastly, the 6-(dimethylamino)purine analogue, 37, was coupled to N-(benzyl-oxycarbonyl)-p-methoxy-L-phenylalanine to provide, after deprotection, the novel puromycin-like analogue 39. The analogues 26-29, 36, and 39 were all evaluated for antitumor and, except for 39, for antiviral activity. These compounds failed to appreciably inhibit the growth of P388 mouse leukemia cells in vitro at concentrations up to 100 micrograms/mL. In addition, they did not exhibit noticeable activity against the human immunodeficiency virus or herpes simplex virus type 1 at concentrations as high as 100 microM. The adenine analogue, 26, did, however, prove to be a substrate for adenosine deaminase. It possessed an affinity for the enzyme only 50% less than that of adenosine with a Ki = 85 microM.
