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Describes architect Frank Gehry and his renegade California style that is going global. Work on his own home in Santa Monica in 1978 that brought him instant notoriety; Once considered a regionalist; How he works on projects; Winning of the Pritzker Prize; Inspiration on a whole generation of younger architects; His cardboard chairs; Why Gehry is suddenly so popular; Description of his personality; More. INSET: Step by step..

Discussion of pop artist Andy Warhol auction to be held beginning on April 23 at Sotheby's in New York. His eclectic collection is expected to become an event that combines beauty and kitsch, spectacle and speculation. Description of items and Sotheby's plans for promotion and sale.

A 61 year old woman presented with a one week history of headache, drowsiness, and shortness of breath. Initial examination revealed bilateral ptosis, which the patient stated had been present [...]

•Multiple sclerosis is diagnosed according to the McDonald Criteria, recently revised in 2017.•Revisions are based on existing evidence, and not expert opinion.•Misdiagnosis in multiple sclerosis remains an issue in recent studies.•High-priority areas of research in multiple sclerosis may influence further diagnostic criteria.

Multiple sclerosis (MS) incidence and prevalence is increasing worldwide, with a disproportionally higher rate in women. Recent studies have questioned the presence of a latitudinal gradient in Europe. Ireland is a high prevalence country for MS with a previously reported North-South gradient making it ideal to further explore this concept.

Discusses the reopening of the Guggenheim Museum in New York City. How it was splendidly restored; Construction of a controversial new edition; Critics who contend that the Guggenheim is less a museum than a monument to it's creator, Frank Lloyd Wright; How in the initial construction the building subverted Wright's intentions.

States that with six new hotels and a theme park outside Paris, the Disney company is an architectural patron par excellence. Descriptions of buildings which are part of Euro Disney; Disney's decision to stick with downhome Americana designs; Critics of Disney's approach.

Examines the cultural explosion in Spain, where the contemporary art scene has taken off, and is quickly becoming international. New generation from every region; Ministry of Culture plays a big role; Incredibly varied public art.

Profiles modernist architect I.M. Pei, 72, known for his attention to details and buildings that exude taste, and talks about his new Morton H. Meyerson Symphony Center in Dallas and its complex design problems. Pei's effects on other designers;Other work; Sons in business; Reputation.

Talks about California architect Frank Gehry, 60, whose work is usually low budget, brash, offbeat, of humble materials, and in geometric shapes. Gehry won the Pritzker Architecture Prize, the profession's most august international award, for his design for a Los Angeles concert hall. Gehry's works; Prize; Career; Personal life.

Talks about the increasing number of million-dollar tract homes and some architects who bring flair and a sense of proportion to such houses, while leaving some options to buyers. Example developments and architects' styles.

Report that landscape painting has been making a surprising comeback in many fashionable galleries and private collections. Most of the contemporary artists, however, don't paint real scenes, but paint from their imagination. New artists and paintings.

Report on the huge Edgar Degas retrospective opening soon at the Metropolitan Museum of Art in New York, N.Y., and the homage it pays to the artist and Impressionism. Degas' career and successes; Show; Era changes.

•There is a trend towards increasing index over time in those with a baseline positive JCV index value.•In patients with baseline negative JCV, the majority remained negative through follow-up.•Rates of seroconversion approximated 5.8% per year, with a median time to seroconversion of 103 months.

Cognitive impairment is common in multiple sclerosis (MS) irrespective of disease stage or subtype. It is typically underreported and neuropsychological testing can be required to detect more subtle evidence of cognitive impairment. The Brief International Cognitive Assessment in Multiple Sclerosis (BICAMS) was an initiative undertaken by a panel of experts with the primary objective of identifying a brief cognitive assessment tool that could be administered by healthcare professionals without formal neuropsychological training to identify early or subtle cognitive impairment among MS patients.

An outbreak of campylobacteriosis affected approximately one-half of 165 people attending an annual farmers' dance in Montrose, Scotland, in November 2005. Epidemiological investigations, including a cohort study (n = 164), identified chicken liver paté as the most likely vehicle of infection. Paté preparation involved deliberate undercooking of chicken livers by flash-frying, followed by mechanical homogenization. Typing of 32 Campylobacter strains (isolated from submitted stools) by multilocus sequence typing identified four distinct clades of Campylobacter jejuni. There was good agreement when isolates were typed by Penner serotyping, pulsed-field gel electrophoresis, and flaA short variable region sequencing but poorer agreement with phage and antibiotic susceptibility testing. At least three attendees were coinfected with two Campylobacter strains each. The outbreak was probably due to several livers contributing Campylobacter strains that survived undercooking and were dispersed throughout the paté. The study highlights improper culinary procedures as a potential human health risk and provides a striking counterexample to the "dominant outbreak strain" view of point source outbreaks of food-borne infections. It also demonstrates that previous exposure to biologically plausible sources of Campylobacter may confer protection against subsequent infection.

ABSTRACTAn outbreak of campylobacteriosis affected approximately one-half of 165 people attending an annual farmers' dance in Montrose, Scotland, in November 2005. Epidemiological investigations, including a cohort study (n= 164), identified chicken liver pate´ as the most likely vehicle of infection. Pate´ preparation involved deliberate undercooking of chicken livers by flash-frying, followed by mechanical homogenization. Typing of 32 Campylobacterstrains (isolated from submitted stools) by multilocus sequence typing identified four distinct clades of Campylobacter jejuni. There was good agreement when isolates were typed by Penner serotyping, pulsed-field gel electrophoresis, and flaAshort variable region sequencing but poorer agreement with phage and antibiotic susceptibility testing. At least three attendees were coinfected with two Campylobacterstrains each. The outbreak was probably due to several livers contributing Campylobacterstrains that survived undercooking and were dispersed throughout the pate´. The study highlights improper culinary procedures as a potential human health risk and provides a striking counterexample to the “dominant outbreak strain” view of point source outbreaks of food-borne infections. It also demonstrates that previous exposure to biologically plausible sources of Campylobactermay confer protection against subsequent infection.

Between April and September 2000, 60 injecting drug users in Scotland died or were hospitalized with severe illness. Laboratory investigations suggested that Clostridium novyi and other bacteria were important aetiological agents. To determine associated environmental/behavioural factors a case-control study was undertaken with 19 ‘definite’ and 32 ‘probable’ cases in Glasgow, Scotland. For every deceased case (n=19), up to three proxy individuals were interviewed. Three controls were identified for each case. Multivariate logistic regression analyses compared (i) all cases and controls; (ii) definite cases and matched controls; (iii) probable cases and matched controls. In all three analyses injecting into muscle or skin and injecting most of the time with a filter used by someone else were the variables most strongly associated with illness. Comparing only muscle-injecting cases and controls, cases were significantly more likely to have injected larger amounts of heroin per average injection than were controls. The findings make an important epidemiological contribution to the understanding of the public health and clinical implications of the contamination of illicit drugs by histotoxic clostridia.

We report the first application of pronucleotide (ProTide) technology to the antiviral agent abacavir (Ziagen), used for the treatment of HIV infection. The phenylmethoxyalaninyl phosphoramidate of abacavir was prepared in good yield in one step. Also prepared was the corresponding phosphoramidate of the guanine nucleoside analogue “carbovir”. The antiviral profile of each of the parent nucleosides was compared to that of the phosphoramidate ProTides. A significant (28- to 60-fold) increase in anti-HIV potency was noted for the ProTide of abacavir but not for that of carbovir. These findings were in agreement with the markedly higher (ca. 37-fold) levels of carbovir triphosphate that are formed in CEM cells upon response to the abacavir ProTide compared with the parent abacavir compound. In contrast the anti-HBV potency of both abacavir and carbovir were improved (10- and 20-fold, respectively) by ProTide formation. As in CEM cells, the abacavir ProTide provided significantly enhanced carbovir triphosphate levels in HepG2 2.2.15 cells over that of the parent nucleoside. On the basis of these data, a series of phosphoramidate analogues with structural variation in the ester and amino acid regions were prepared and their antiviral profiles described. In addition, the pharmacokinetic disposition of the abacavir phenylethoxyalaninyl phosphoramidate was evaluated in Cynomolgus monkeys.

Following our discovery of the potent anti-varicella zoster virus action of lipophilic alkyl furano pyrimidine 2‘-deoxynucleosides, we now report that 2‘,3‘-dideoxy sugar analogues are devoid of anti-VZV activity but are potent and selective inhibitors of human cytomegalovirus (HCMV). The present compounds are active in vitro at ca. 1 μM with cytotoxicity only above 200 μM. Importantly, we have discovered that the new agents do not act as nucleoside analogues, despite their nucleosidic structure, and time of addition studies revealed that the compounds may inhibit HCMV at an event in the replication cycle of the virus that precedes DNA synthesis. They represent new leads in the discovery of improved therapies for HCMV, particularly in view of their novel mechanism of action.

We have previously reported the discovery and preliminary structure-activity relationships of a new class of inhibitors of varicella-zoster virus (VZV). These novel furanopyrimidine nucleosides bear unusual bicyclic base moieties and exhibit complete specificity for VZV. Limited in vitrocytotoxicity has been detected and the bicyclic nucleosides are now well established as a new family of potent antivirals. Our initial studies revealed an absolute requirement of a long alkyl side-chain, with an optimal chain length of C8-C10, for antiviral activity. Following further studies, we recently reported a significant enhancement of both antiviral potency and selectivity by the inclusion of a phenyl group within the alkyl side-chain of these compounds. The new lead p-alkylphenyl analogues displayed EC50values below 1 nM versus VZV and selectivity index values >1000000. We herein report the synthesis and characterization of a further series of alkylaryl analogues bearing terminal phenyl groups with varying n-alkyl side-chain lengths. Synthesis of the target bicyclic systems involved the Pd-catalysed coupling of terminal acetylenes with 5-iodo-2′-deoxyuridine to give intermediate 5-alkynyl nucleosides which were then cyclized in the presence of copper (I) iodide. The current compounds display excellent selectivity for VZV with no detectable in vitrocytotoxicity but despite being chemically isomeric with the previous lead p-alkylphenyl analogues, the compounds reported herein exhibit only moderate antiviral activities. A possible correlation between antiviral activity and conformational freedom of the side-chain is discussed.

We report the design, synthesis and antiviral evaluation of a number of lipophilic, masked phosphoramidate derivatives of the antiherpetic agent (E)-5-(2-bromovinyl)-2′-deoxyuridine (BVDU), designed to act as membrane soluble prodrugs of the free nucleotide. The phosphoramidate derivatives of BVDU that contain L-alanine exhibited potent anti herpes simplex virus type 1 and varicella-zoster virus activity but lost marked activity against thymidine kinase-deficient virus strains. The phosphoramidate derivative bearing the amino acid α,α-dimethylglycine showed poor activity in all cell lines tested. It appears that successful kinase bypass by phosphoramidates is highly dependent on the nucleoside analogue, amino acid and ester structure, as well as the cell line to which the drugs are exposed.

We have recently reported the discovery of an entirely new category of potent antiviral agents based on novel deoxynucleoside analogues with unusual fluorescent bicyclic furano base moieties. In order to probe structure activity relationships we prepared a series of 5-aryl derivatives of the lead structures. We herein report the synthesis, characterization, and antiviral evaluation of these novel compounds. 5-Aryl derivatives of the parent nucleosides were synthesized from the corresponding alkynyl deoxyuridines using a simple, versatile and efficient one-step conversion, based on a palladium-catalysed cyclization. As previously noted for the lead compounds, a long alkyl side-chain on the base moiety is essential for antiviral activity. Even with the optimal (C8-C10) side-chain, most of the present compounds are markedly less active than their parent structures. However, some of the synthesized compounds still retained antiviral activity at non-cytotoxic concentrations, being only two- to fivefold less active than the current clinical agent acyclovir. Possible reasons for this structure activity relationship are discussed.

Bicyclic furano pyrimidine nucleosides have been found to be highly potent and selective inhibitors of varicella zoster virus (VZV). They are inactive against herpes simplex virus and have been known for several decades as (unwanted) synthetic by-products in the Pd-catalysed coupling of acetylenes to 5-iodo nucleosides. These fluorescent bicyclic nucleosides are now established as a new family of potent antivirals. They are unusual in that they exhibit complete specificity for VZV and require an alkyl (or alkylaryl) side-chain for biological activity. The latter requirement confers extremely high lipophilicities on these compounds, unknown amongst chemotherapeutic nucleosides, which may be of considerable importance in formulation, dosing and tissue distribution. The most potent compounds reported are p-alkylaryl compounds, with EC50values below 1nM versus VZV and selectivity index values of around 1000000. Here, we review the discovery, synthesis, characterization, antiviral profile, SAR, mechanism of action and development prospects for this new family of antivirals.

In addition to our recent report on the potent anti-varicella-zoster virus (VZV) activity of some unusual bicyclic furopyrimidine nucleosides bearing long alkyl side chains, we herein report the further significant enhancement of the antiviral potency by inclusion of a phenyl group in the side chain of these compounds. The target structures were prepared by the Pd-catalyzed coupling of a series of para-substituted arylacetylenes with 5-iodo-2‘-deoxyuridine, to give intermediate 5-alkynyl nucleosides which were cyclized in the presence of Cu to give the desired bicyclic systems. The compounds display extraordinary potency and selectivity for VZV; the most active are ca. 10 000 times more potent than the reference compound acyclovir and ca. 100 times more potent than the alkyl analogues earlier reported by us. The current compounds show little cytotoxicity, leading to selectivity index values  1 000 000. From a range of DNA and RNA viruses tested, only VZV was inhibited by these compounds indicating their extreme selectivity for this target virus. The novelty of the molecules, coupled with their extreme potency and selectivity, their desirable physicochemical properties, and their relative ease of synthesis, makes them of considerable interest for potential drug development for VZV infections.

We have recently reported the discovery of an entirely new category of potent anti-varicella-zoster virus agents based on novel deoxynucleoside analogues bearing unusual fluorescent bicyclic furo base moieties. Initial studies revealed an absolute requirement of a long alkyl side-chain, with an optimal length of C8–C10, for antiviral activity. However, the impact of this requirement on the physical properties of these compounds is high: inherent lipophilicity and extremely poor aqueous solubility, which may limit the use of these nucleosides as drugs. In order to address this issue, we have now prepared a new series of analogues, bearing ether and glycol type side-chains, designed to improve the aqueous solubility of the compounds. Synthesis of target nucleosides involved Pd-catalysed coupling of terminal alkynes with 5-iodo-2′-deoxyuridine. The 5-alkynyl nucleosides thus obtained were then treated with copper (I) iodide to produce the desired bicyclic analogues. As anticipated, the new compounds exhibited a dramatic increase in aqueous solubility, although antiviral activity was significantly reduced. A possible correlation between antiviral activity and overall compound lipophilicity is discussed.

We have recently reported the discovery of an entirely new category of potent antiviral agents based on novel deoxynucleoside analogues with unusual fluorescent bicyclic furo base moieties. To probe structure-activity relationships and to seek to optimize the properties of the lead compounds, we prepared pyrro analogues of the furo systems. We herein report the synthesis, characterization and antiviral evaluation of these novel compounds.

The anti-human immunodeficiency virus (HIV) activity of aryloxyphosphoramidate protides of a number of anti-HIV nucleoside analogues was assessed in resting primary monocyte-macrophages (M/M). While 2',3'-dideoxythymidine (d4T), 2',3'-dideoxyadenosine (ddA), and 2',3'-dideoxy-2',3'-didehydroadenosine (d4A) protides showed an anti-HIV activity that was 25- to 625-fold greater than the parent nucleotides d4T, ddA, and d4A, respectively, other aryloxyphosphoramidate protides showed similar or even lower anti-HIV activities than their parent compounds. This variable anti-HIV effect is most likely related to the different dynamics of intracellular nucleoside monophosphate release from the protides. Our results indicate the potential advantage of therapeutic use of this approach for some nucleotide analogues to affect HIV replication in M/M, one of the major reservoirs of HIV in vivo.

We herein report the discovery of an entirely new category of potent antiviral agents based on novel deoxynucleoside analogues with unusual bicyclic base moieties. Target structures, previously known as byproducts in Pd-catalyzed coupling of terminal alkynes with 5-iodo-nucleosides, are recognized herein for the first time to be potent and selective inhibitors of varicella-zoster virus (VZV) in vitro. As an unusual structure−activity relationship we noted the absolute requirement of a long alkyl side chain, with an optimum length of C8−C10, for antiviral activity. We thus report the synthesis and characterization of a series of chain-modified analogues and their extensive in vitro evaluation. The lead compounds have a ca. 300-fold enhancement in anti-VZV activity over the reference compound acyclovir, with no detectable in vitro cytotoxicity. The novel structure of these compounds, coupled with their ease of synthesis, excellent antiviral profile, and promising physical properties, makes them of great interest for possible antiviral drug development.

A series of new substituted-aryl phosphoramidate derivatives of the anti-HIV drug d4T were synthesized as membrane-soluble nucleotide prodrugs, to extend and quantify the SAR observed for an earlier series of related derivatives. All of the compounds were found to be significantly more potent against HIV in cell culture than the nucleoside analogue d4T, and most were also found to be significantly more potent than the parent phosphoramidate. A Hansch type QSAR analysis was applied to the combined series of 21 compounds. The results of this analysis revealed anti-HIV activity to be principally dependent on lipophilicity in a quadratic manner, with terms representing substituent steric bulk and electronic effects having a minimal significance.

New substituted-aryl phosphoramidate derivatives of the anti-HIV drug d4T were synthesized as membrane-soluble intracellular prodrugs for the free bioactive phosphate to establish relationship(s) between compound structure and in vitro antiviral activity. The majority of compounds demonstrated an elevation of in vitro potency relative to that of the parent nucleoside, and unlike d4T, all retained full activity in thymidine kinase-deficient cells. The compound bearing a p-chloro aryl group (8e) expressed nanomolar activity in vitro, a 14-fold increase in activity relative to that of the unsubstituted phosphoramidate (100-fold compared to d4T). An assay using pig liver esterase was used to establish the stability of the compounds to enzymatic degradation. While there was no apparent correlation between in vitro activity and half-life of enzymatic degradation, there was a close correlation between compound lipophilicity, determined by octanol/water partition coefficient, and in vitro potency. We suggest that substitutions made to the aryl moiety of the aryl phosphoramidate of d4T that result in enhancing lipophilicity may serve to increase the cellular uptake of the prodrug by passive diffusion, leading to the expression of antiviral potency at reduced prodrug concentrations.

We report the design, synthesis and antiviral evaluation of a series of lipophilic, masked phosphoramidate derivatives of the anti-human immunodeficiency virus (HIV) nucleoside analogue d4T, designed to act as membrane-soluble prodrug forms for the free nucleotide. In particular, we report a series of 12 novel compounds with systematic variation in the structure of the carboxylate ester function. In order to rationalize the changes in antiviral action with variation of this moiety we applied our recently developed 31P NMR-based assay for carboxyesterase lability to this series. However, no clear positive correlation emerged, indicating that, at least within this series, factors other than simple esterase lability may be the major determinants of antiviral potency.

A series of U4 and U6 snRNA mutants was analysed in Xenopus oocytes to determine whether they block splicing complex assembly or splicing itself. All the U4 and U6 mutants found to be inactive in splicing complementation resulted in defects in assembly of either U4/U6 snRNP or of splicing complexes. No mutants were found to separate the entry of U5 and U6 snRNAs into splicing complexes and neither of these RNAs was able to associate with the pre‐mRNA in the absence of U4. In the absence of U6 snRNA, however, U4 entered a complex containing pre‐mRNA as well as the U1 and U2 snRNAs. U6 nucleotides whose mutation resulted in specific blockage of the second step of splicing in Saccharomyces cerevisiae are shown not to be essential for splicing in the oocyte assay. The results are discussed in terms of the roles of U4 and U6 in the assembly and catalytic steps of the splicing process.

Recombinant baculoviruses were used to express wild‐type serum response factor (SRF) and a mutant, SRF.CKIIA, which lacks all four serine residues in the major casein kinase II (CKII) site at residues 77–90. Purified recombinant SRF binds DNA with an affinity and specificity indistinguishable from that of HeLa cell SRF, and activates transcription in vitro. Comparative phosphopeptide analysis of the wild‐type and mutant proteins demonstrated that the wild‐type protein is phosphorylated at the major CKII site in insect cells. Dephosphorylation of recombinant SRF does not affect its affinity for the c‐fos SRE, and results in only a 3‐fold reduction in binding to the synthetic site ACT.L. However, dephosphorylation does cause a large decrease in the rates of association with and dissociation from either site. These effects are due solely to phosphorylation at the major CKII site: the binding properties of the SRF.CKIIA mutant are identical to those of dephosphorylated wild‐type SRF, and CKII phosphorylation in vitro converts dephosphorylated wild‐type SRF from a slow‐binding to a fast‐binding form without significantly changing binding affinity. CKII phosphorylation thus acts to potentiate SRF‐DNA exchange rates rather than alter equilibrium binding affinity.

Structure‐function relationships in the vertebrate U4‐U6 snRNP have been analysed by assaying the ability of mutant RNAs to form U4‐U6 snRNPs and to function in splicing complementation in Xenopus oocytes. The mutants define three categories of domain within the RNAs. First, domains which are not essential for splicing. These include regions of U6 which have previously been implicated in the capping and transport to the nucleus of U6 RNA as well as, less surprisingly, regions of U4 and U6 which have been poorly conserved in evolution. Second, domains whose mutation reduces U4‐U6 snRNP assembly or stability. This group includes mutations in both the proposed U4‐U6 interaction domain, and also, in the case of U6, in a highly conserve sequence flanking stem I of the interaction domain. These mutants are all defective in splicing. Third, regions not required for U4‐U6 assembly, but required for splicing complementation. This category defines domains which are likely to be required for specific contacts with other components of the splicing machinery. Combinations of mutants in the U4 and U6 interaction domain are used to show that there are not only requirements for base complementarity but also for specific sequences in these regions.

Novel phosphoramidate derivatives of the anti-HIV nucleoside analogues AZT and d4T have been prepared by phosphorochloridate chemistry. These materials are designed to act as labile membrane-soluble prodrugs of the bio-active free nucleotides. All compounds were fully characterised by a range of methods and were subjected to evaluation in vitroof their anti-HIV efficacy. A notable feature of the current study was that any attempt to replace the amino acid moiety of the phosphoramidate with a simple amine lead to a marked, virtually total loss of activity. Such simple phenyl alkylamino phosphate derivatives of either d4T or AZT inhibit HIV replication at cytotoxic concentrations and have no detectable antiviral selectivity. This clearly highlights the vital role played by the amino acid in the antiviral efficacy of the blocked phosphoramidates.

Novel symmetrical nucIeotide-(5′,5′)-dimers of 3′-O-acetylthymidine, 3′-O-methylthymidine, 3′-O-ethylthymidine, 3′-O-n-propylthymidine and 3′-azido-3′-deoxythymidine (AZT) were synthesized as membrane soluble pro-drugs. These were prepared using phosphorodichloridate chemistry and were characterised by spectroscopic and analytical data. In-vitro evaluation of the derivatives in cells acutely infected with the human immunodeficiency virus (HIV-1) demonstrated a range of activities. These derivatives were generally found to display poor inhibition of HIV proliferation. Derivatives containing AZT moieties were found to be potent, but such compounds were less active than the parent nucleoside. The data indicated that the AZT-containing compounds act primarily via the release of the free nucleoside. However, in some cases, the dimers of certain inactive nucleoside analogues were found to be active. In these cases, release of the nucleoside alone cannot account for the activity.

The reaction of thymidine, AZT (Fig. 1, compound 1) and ddCyd (Fig. 1, compound 2) with bis(2,2,2-trichloroethyl) phosphorochloridate gave novel 5′-bis(2,2,2-trichloroethyl) phosphates, characterized by spectroscopic and analytical data. Analogous reactions with bis(2,2,2-trifluoroethyl) phosphorochloridate gave the corresponding AZT and ddCyd derivatives. In both of the ddCyd reactions, by-products were isolated and characterized as O5′, W4-diphosphorylated materials. It was hoped that the 5′-phosphate triesters might act as membrane-soluble pro-drugs of the bio-active free nucleotides of AZT or ddCyd. In fact, all of the 5′-phosphate derivatives of AZT and ddCyd displayed anti-HIV activity in vitro.Surprisingly, the thymidine compound also displayed very slight anti-HIV activity. The striking activity of the AZT and ddCyd derivatives is attributed to the metabolic instability of the substituted trialkyl phosphate moiety.

Novel phosphoramidate derivatives of the anti-HIV nucleoside analogue d4T were designed to act as labile membrane-soluble prodrugs of the bio-active free nucleotide d4TMP. We herein reveal the very marked dependence of the antiviral activity of these phosphoramidates upon the stereochemistry of the amino acid attached to the phosphate centre; with a strong preference for the L-stereochemistry. These phosphate triesters were shown to liberate amino acid derivatives of the nucleotide intracellularly. These novel analogues, typified by alaninyl d4T monophosphate, may act as intracellular sources of the free nucleotides. The alaninyl d4T adducts themselves exert an antiviral effect when administered extracellularly, but again with clear distinctions between the L- and D-series. This evidence indicates that extracellularly administered blocked triesters derived from L-amino acids can generate d4TMP intracellularly, by a new pathway which is highly dependent on the amino acid stereochemistry.

The reaction of 3′-azido-3′-deoxythymidine (AZT) with phosphoryl chloride followed by amino acid methyl esters gave novel diamidate derivatives of AZT 5′-monophosphate (AZTMP). It was hoped that the 5′-phosphorodiamidates might act as membrane-soluble prodrugs of the bio-active free nucleotides of AZT. Five different amino acids were employed, covering a range of structures and polarities. The reaction was also conducted with propylamine, and with diethylamine. The derivatives were tested for their inhibitory effect on human immunodeficiency virus type 1 (HIV-1) proliferation in a human lymphoblastoid cell line. The amino acid derivatives were potent inhibitors of viral proliferation, small changes in structure leading to marked changes in activity.

A series of monophosphate triester derivatives of 3′-azido-3′-deoxythymidine (AZT), designed as membrane-soluble pro-drugs of the nucleotide (AZTMP), have been tested for activity against the human immunodeficiency virus (HIV-1). It has been found that when carboxyl-protected, amino-linked amino acids, and alkyl chains, are asymmetrically substituted on the 5′-phosphate a significant antiviral effect is observed. Moreover, the activity of the compounds is profoundly dependent on the structure of the phosphate moiety, and in particular on the nature of the amino acid.

Novel chain-extended nucleoside phosphoramidates of the anti-human immunodeficiency virus (HIV) drug d4T (stavudine) have been prepared as possible membrane-permeable prodrugs of the bio-active free 5′-monophosphates. Phosphorochloridate chemistry gave the target compounds in moderate to high yields, and all materials were fully characterized by spectroscopic and analytical methods. The compounds are related to the previously reported phenyl methoxyalaninyl derivative of d4T, which was shown to be a potent and selective inhibitor of HIV. In this study theamino acid nitrogen and ester moieties were separated by methylene spacers of between two and six carbon atoms. In vitroevaluation of these compounds indicated an almost complete lack of anti-HIV activity, the compounds being several orders of magnitude less potent than the corresponding α-amino acid derivatives. The reasons for the virtual lack of anti-HIV activity appear to involve poor enzyme-mediated hydrolysis.

A number of symmetric and asymmetric 5′-phosphate esters of the potent anti-varicellazoster virus (VZV) agent 1–(β-d-arabinofuranosyl)-5-prop-1-ynyluracil (882C; netivudine) were prepared as potential lipophilic, membrane-soluble prodrugs of the bioactive phosphate forms. The compounds were prepared by the base-catalysed coupling of various phosphorochloridates with the free nucleoside analogue. Compounds were fully characterized by a range of spectroscopic and analytical methods and were studied for their inhibition of several viruses in tissue culture. All of the phosphate esters were inactive against human cytomegalovirus, herpes simplex virus type 2, VZV, human immunodeficiency virus type 1 and influenza A virus (EC50>100 μM) except the 5′-(4–nitrophenyl phenyl) phosphate, which inhibited influenza A virus. The relative rate of esterase-mediated hydrolysis of one of the lead target structures was measured in order to rationalize the poor antiviral action, and data were collected on possible metabolites in support of this analysis. Cell-specific esterases are implicated as key determinants of the antiviral potency of prodrugs of this type.