Synthesis and influenza virus sialidase inhibitory activity of analogues of 4-Guanidino-Neu5Ac2en (Zanamivir) modified in the glycerol side-chain.

Analogues of 4-Guanidino-Neu5Ac2en (Zanamivir) have been prepared containing carbamate substituents at the 7-hydroxy position. (4S,5R,6R)-5-Acetylamino-6-[1R-[(6-aminohexyl)carbamoyloxy]-2R,3-dihydroxypropyl]-4-guanidino-5,6-dihydro-4H-pyran-2carboxylic acid and (4S,5R,6R)-5-Acetylamino-6-[1R-[heptylcarbamoyloxy]-2R,3-dihydroxypropyl]-4-guanidino-5,6-dihydro4H-pyran2-carboxylic acid were the two analogues possessing activity comparable to Zanamivir, showing potent inhibition of influenza virus sialidases and good antiviral activity in vitro.

Benzophenone derivatives: a novel series of potent and selective inhibitors of human immunodeficiency virus type 1 reverse transcriptase.

A series of benzophenone derivatives has been synthesized and evaluated as inhibitors of HIV-1 reverse transcriptase (RT) and the growth of HIV-1 in MT-4 cells. Through the use of the structure-activity relationships within this series of compounds and computational chemistry techniques, a binding conformation is proposed. The SAR also indicated that the major interactions of 1h with the RT enzyme are through hydrogen bonding of the amide and benzophenone carbonyls and pi-orbital interactions with the benzophenone nucleus and an aromatic function separated from the benzophenone by a suitable spacer group. The crystal structure of compound 1h has been determined. A number of compounds with potent inhibitory activity against HIV-1 RT and HIV in cellular assays at levels comparable with AZT and our efforts to identify a metabolically stable analogue are described.

Discovery and analysis of a series of C2-symmetric HIV-1 proteinase inhibitors derived from penicillin.

In order to identify a suitable peptide substrate for human immunodeficiency virus-1 (HIV-1) proteinase, a range of peptides from various cleavage sites within the gag-pol polyprotein were assayed by HPLC for specific cleavage. The peptide with the optimal combination of favorable kinetics and good solubility was based on the N-terminus cleavage site of HIV-1 proteinase (KQGTVSFNF*PQIT). The HPLC assay, using the above peptide, was developed into a rapid isocratic method in order to analyze inhibition kinetics. An assay suitable for high-throughput screening was developed using a radioactively labeled peptide with the same sequence, coupled to a solid phase. Using this assay, a C2-symmetric HIV-1 proteinase inhibitor derived from penicillin was discovered during random screening of a compound library. A chemical synthesis program developed this structure into a series of potent inhibitors. The lead structures were highly selective for HIV-1 proteinase with good antiviral activity in vitro against HIV and no cytotoxicity. The HPLC assay was used to demonstrate that these compounds are competitive tight-binding inhibitors of HIV-1 proteinase.

A series of penicillin derived C2-symmetric inhibitors of HIV-1 proteinase: synthesis, mode of interaction, and structure-activity relationships.

The C2-symmetric diester 1 was identified by random screening as a novel inhibitor of HIV-1 proteinase. This led to the preparation of a series of related more potent amides from readily accessible penicillins. Many of the compounds showed potent antiviral activity in HIV-1-infected MT-4 cells and an ability to inhibit syncytia formation in infected C8166 cells, with no evidence of cytotoxicity. The compounds showed no activity against other aspartyl proteinases (renin, pepsin, and cathepsin D). Structure-activity relationships support a symmetrical interaction with the enzyme. Pharmacokinetic evaluation of the ethylamide 3 revealed it was subject to rapid plasma clearance and had low oral bioavailability.

Expression of atrial natriuretic factor as a cleavable fusion protein with chloramphenicol acetyltransferase in Escherichia coli.

Recombinant fusion proteins containing human atrial natriuretic factor, ANF(1-28) joined to chloramphenicol acetyltransferase (CAT) via cleavable linker sequences have been produced in Escherichia coli. The linker sequences were designed to allow the release of authentic ANF(1-28) following proteolytic cleavage by enterokinase or thrombin, or chemical cleavage with 2-(2-nitrophenylsulphenyl)-3-methyl-3'-bromoindolenine. Proteins, containing ANF(1-28) fused to the carboxyl-terminal region of CAT (using the ScaI restriction site in the cat gene), were largely soluble in E. coli and were obtained in higher yield than analogues containing ANF(1-28) linked to shorter CAT sequences. The longer derivatives also retained CAT activity allowing subsequent purification by affinity chromatography.

Synthesis and biological activity of some cardiotonic compounds related to gitoxigenin.

The four diastereomeric 3,16-diacetates 6, 9, 10 and 11 were prepared from gitoxin 1 by the routes shown in Schemes 1 and 2 and tested for inotropic activity in the isolated guinea-pig atrial preparation. In line with earlier findings in the digitoxigenin series, derivatives with a 3 alpha-acetoxy function, viz 9 and 10, possessed high biological activity.

Synthesis and biological activity of some cardiotonic compounds related to digitoxigenin.

3 beta-Amino compounds with 17 beta-(3-furyl) and (4-pyridazinyl) ring systems were prepared from digitoxigenin 1b and found to have similar cardiotonic properties to the analogous 3 beta-hydroxy compounds when tested in the isolated guinea-pig atrial preparation. Derivatives with 3 alpha-acetoxy functions were found to have higher than expected activities. Particularly potent was the pyridazine N1-oxide 19. All isocardenolides and the unsaturated anhydride 18 were devoid of activity.

Synthesis and biological activity of some 3-amino compounds related to digoxigenin.

3 alpha-Amino 1a and 3 beta-amino 1b analogues of digoxigenin 14 and their 12 beta-acetate derivatives 2a and 2b were prepared and tested for inotropic activity in the isolated guinea-pig atrial preparation. The 3 alpha-amino compounds were inactive whereas the 3 beta-amino compounds showed comparable activity to their 3 beta-hydroxy counterparts. The replacement of the 17 beta-butenolide ring by other ring systems was investigated. Compounds with a 3'-furyl ring, 9b and 16 were found to possess appreciable activity. A compound with a 4'-pyridazinyl ring 13b exhibited weak activity, whereas the isomeric butenolide compound 11b proved inactive. N-monomethylation of the amine 2b reduced activity and N-dimethylation abolished activity. Acetylation of the 12 beta-hydroxyl function gave less active compounds.

A new series of steroidal antidysrhythmic agents.

With the aim of finding an antidysrhythmic agent suitable for intravenous or oral administration we have examined a range of steroids carrying basic substituents. The primary screen involved control of cardiac dysrhythmias induced by intravenous infusion of aconitine into pentobarbitone-anaesthetised artificially-respired rats. The best activity was found among a series of 11 alpha-alkylamino steroids and structure-activity studies included modification of the alkylamino group and variation of substituents in ring A and at the 17-position. Good oral and intravenous activity was found among 17 beta-methoxycarbonyl-5 alpha-androstanes and methyl 2 beta-ethoxy-3 alpha-hydroxy-11 alpha-(3-methylbutylamino)-5 alpha-androstane-17 beta-carboxylate hydrochloride (CCI 22277) was selected for more detailed pharmacological study.