SummaryEighteen amino acid esters of the antiherpetic drug, acyclovir, were synthesized as potential prodrugs for oral administration. The esters were examined for in vitro antiviral activity against herpes simplex virus Type 1 (HSV-1). They were found to have less potency than the parent compound. Their efficiencies as prodrugs were evaluated in rats by measuring the urinary recovery of acyclovir. Ten prodrugs produced greater amounts of the parent drug in the urine. The L-amino acid esters were better prodrugs than the corresponding D-or D,L-isomers, suggesting the involvement of a stereoselective transporter. The L-valyl ester, 256U87, was the best prodrug. Sixty three per cent of its administered dose was excreted as acyclovir in the urine, a considerable improvement over acyclovir itself, for which this value was 19%. Since 256U87 was stable in aqueous solutions, its conversion to acyclovir in vivo was probably enzyme catalyzed. This L-valyl ester prodrug of acyclovir is now undergoing clinical evaluation.

No abstract

A series of 2-amino-5-arylthiobenzonitriles (1) was found to be active against HIV-1. Structural modifications led to the sulfoxides (2) and sulfones (3). The sulfoxides generally showed antiviral activity against HIV-1 similar to that of 1. The sulfones, however, were the most potent series of analogues, a number having activity against HIV-1 in the nanomolar range. Structural-activity relationship (SAR) studies suggested that a meta substituent, particularly a meta methyl substituent, invariably increased antiviral activities. However, optimal antiviral activities were manifested by compounds where both meta groups in the arylsulfonyl moiety were substituted and one of the substituents was a methyl group. Such a disubstitution led to compounds 3v, 3w, 3x, and 3y having IC50 values against HIV-1 in the low nanomolar range. When gauged for their broad-spectrum antiviral activity against key non-nucleoside reverse transcriptase inhibitor (NNRTI) related mutants, all the di-meta-substituted sulfones 3u-z and the 2-naphthyl analogue 3ee generally showed single-digit nanomolar activity against the V106A and P236L strains and submicromolar to low nanomolar activity against strains E138K, V108I, and Y188C. However, they showed a lack of activity against the K103N and Y181C mutant viruses. The elucidation of the X-ray crystal structure of the complex of 3v (739W94) in HIV-1 reverse transcriptase showed an overlap in the binding domain when compared with the complex of nevirapine in HIV-1 reverse transcriptase. The X-ray structure allowed for the rationalization of SAR data and potencies of the compounds against the mutants.

The design of rigid cyclic analogues derived from cinnamamide 1, (E)-N-cyclopropyl-3-(3-fluorophenyl)prop-2-enamide, and beta-methylcinnamamide 2, (E)-N-cyclopropyl-3-(3-fluorophenyl)but-2-enamide, has led to the discovery of the potent, centrally acting muscle relaxant (E)-2-(4,6-difluoro-1-indanylidene)acetamide, 17. Compound 17 also possesses potent antiinflammatory and analgesic activity. This paper describes the synthesis and the muscle relaxant, antiinflammatory, and analgesic structure-activity relationships of 17 and 67 of its analogues. Compound 17 has been taken into phase I clinical trials.

Endopolygalacturonase [poly(1,4-α-galacturonide) glycanohydrolase EC 3.2.1.151 occurs in tomato fruit in three molecular forms- PG1, PG2A, PG2B. Trace amounts of PG1, 1-10 pkat g-1 are shown to occur in mature-green fruit as compared to 17 nkat in ripe fruit. As polygalacturonase activity increases through ripening, the percentage of the activity due to PG1 decreases progressively from 100 to less than 20. On fully or partly demethylated substrates, PG1 is more active than PG2 when the ionic strength is that expected in the tissue apoplast. A method for purifying PGI from ripe fruit is described. PG1 preparations contain polypeptides of Mr 45, 43 and 38 thousand. The Mr 43 thousand and 45 thousand components correspond in size to PG2A and PG2B and are detected by antisera raised against PG2A. The M, 38 thousand polypeptide is immunologically distinct. From carbohydrate and amino acid analyses, this polypeptide appears to contain 2870 carbohydrate as glucosamine, mannose, xylose and fucose attached to a polypeptide of estimated Mr 28 342 that is rich in tyrosine and glycine. A method for purifying the subunits of PG1 by cation exchange chromatography in 6 M urea is described. PG2A and PG2B were separated by column chromatography and shown to have identical N-terminal sequences, and serine at the C-terminus. PG2A and PG2B are confirmed as two glycoforms of the one polypeptide. The possibility that PGl consists of populations of molecules containing either PG2A or PG2B coupled with the Mr 38 thousand polypeptide is discussed.

Oxidative cyclization of benzyltetrahydroisoquinolines has long been considered as a biogenetic route to aporphine alkaloids.2 In 1957, Barton and Cohen3 suggested that phenolic oxidation of diphenolic benzyltetrahydroisoquinoline precursors may generate the bond between the aporphine rings A and D, and this proposal has been amply supported by the results of numerous subsequent biosynthetic and synthetic studies.4'5 We wish to report herewith a second oxidative route, efficient intramolecular coupling of monophen-(1) This investigation was supported by a grant from the National Cancer Institute (CA-12059).(2) R. Robinson, "The Structural Relations of Natural Products," Clarendon, Oxford, 1955, and numerous earlier references cited therein.

No abstract

A series of 1-[(2-hydroxyethoxy)methyl]-5-benzyluracils were synthesized and tested for inhibition of murine liver uridine phosphorylase (UrdPase). Inhibitors of UrdPase are reported to enhance the chemotherapeutic utility of 5-fluoro-2'-deoxyuridine and 5-fluorouracil and to ameliorate zidovudine-induced anemia in animal models. We prepared a series of 5-aryl-substituted analogues of 5-benzylacyclouridine (BAU), a good inhibitor of UrdPase (IC50 of 0.46 microM), to develop a compound with enhanced potency and improved pharmacokinetics. The first phase of structure-activity relationship studies on a series of 32 aryl-substituted 5-benzyluracils found several 5-(3-alkoxybenzyl) analogues of 5-benzyluracil with enhanced potency. The acyclovir side chain, the (2-hydroxyethoxy)methyl group, was substituted on the more potent aryl-substituted 5-benzyluracils. The two most potent compounds, 10y (3-propoxy) and 10dd (3-sec-butoxy), were inhibitors of UrdPase with IC50s of 0.047 and 0.027 microM, respectively. Six compounds were tested in vivo for effects on steady-state concentrations of circulating uridine in rats. Plasma uridine levels were elevated 3-9-fold by compound levels that ranged from 8 to 50 microM.