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Great pioneers of nucleic acid chemistry had elucidated nucleic acid functions and structures and developed various antiviral modified nucleoside drugs. It is possible in theory that antiviral modified nucleosides prevent viral replication by inhibiting viral polymerases. However, biological phenomena far exceed our predictions at times. We describe the characteristics of the approved antiviral modified nucleosides from an organic chemistry perspective. Also, based on our experiences and findings through the development of the HIV-1 reverse-transcriptase inhibitor "Islatravir", we provide the practical and approximate guidelines for the drug development of antiviral modified nucleosides against COVID-19., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) and 4'-ethynyl-2'-deoxyadenosine (EdA) are nucleoside analogues which inhibit human immunodeficiency virus type 1 (HIV-1) reverse transcriptase. EdAP, a cyclosaligenyl (cycloSal) phosphate derivative of EdA, inhibits the replication of the influenza A virus. The common structural feature of these compounds is the ethynyl group at the 4'-position. In this study, these nucleoside analogues were prepared by a common synthetic strategy starting from the known 1,2-di- O -acetyl-D-ribofuranose. Biological evaluation of EdAP revealed that this compound reduced hepatitis B virus (HBV) replication dose-dependently without cytotoxicity against host cells tested in this study.

Influenza A viruses leading to infectious respiratory diseases cause seasonal epidemics and sometimes periodic global pandemics. Viral polymerase is an attractive target in inhibiting viral replication, and 4'-ethynyladenosine, which has been reported as a highly potent anti-human immunodeficiency virus (HIV) nucleoside derivative, can work as an anti-influenza agent. Herein, we designed and synthesized a 4'-ethynyl-2'-deoxyadenosine 5'-monophosphate analog called EdAP ( 5 ). EdAP exhibited potent inhibition against influenza virus multiplication in Madin-Darby canine kidney (MDCK) cells transfected with human α2-6-sialyltransferase (SIAT1) cDNA and did not show any toxicity toward the cells. Surprisingly, this DNA-type nucleic acid analog ( 5 ) inhibited the multiplication of influenza A virus, although influenza virus is an RNA virus that does not generate DNA.

Background: The inverse relationship between HDL cholesterol and cardiovascular mortality is weakened in coronary artery disease (CAD). We aimed to investigate the associations of HDL particle concentrations with cardiovascular mortality and the impact of CAD on these associations. We also sought to comparatively evaluate HDL cholesterol and HDL particle concentrations in predicting cardiovascular mortality., Methods: Total and subclass HDL particle concentrations were measured by nuclear magnetic resonance spectroscopy in 2290 participants of the LUdwigshafen RIsk and Cardiovascular Health study referred for coronary angiography. The participants were prospectively followed over a median (interquartile range) duration of 10.0 (6.1-10.6) years., Results: The mean (SD) age of the participants (1575 males, 715 females) was 62.9 (10.4) years; body mass index, 27.6 (4.1) kg/m 2 ; HDL cholesterol, 39 (11) mg/dL [1 (0.29) mmol/L]; and total HDL particle concentration, 24.1 (5.8) μmol/L. Of the participants, 434 died from cardiovascular diseases. In multivariate analyses, tertiles of total HDL particle concentrations were inversely related to cardiovascular mortality (hazard ratio for third vs first tertile = 0.55, P < 0.001). This association was primarily mediated by small HDL particles ( P < 0.001). Adding total or small HDL particle concentrations rather than HDL cholesterol to multivariate prediction models improved performance metrics for cardiovascular mortality. The presence of CAD had no impact on the associations between HDL particle concentrations and cardiovascular mortality., Conclusions: High HDL particle concentration is consistently and independently of CAD associated with decreased cardiovascular mortality. Whether the inverse relationship between HDL particle concentration and cardiovascular mortality may be translated into novel therapies is under investigation., (© 2017 American Association for Clinical Chemistry.)

The design, synthesis and application of N-acetylneuraminic acid-derived compounds bearing anomeric sulfo functional groups are described. These novel compounds, which we refer to as sulfo-sialic acid analogues, include 2-decarboxy-2-deoxy-2-sulfo-N-acetylneuraminic acid and its 4-deoxy-3,4-dehydrogenated pseudoglycal. While 2-decarboxy-2-deoxy-2-sulfo-N-acetylneuraminic acid contains no further modifications of the 2-deoxy-pyranose ring, it is still a more potent inhibitor of avian-origin H5N1 neuraminidase (NA) and drug-resistant His275Tyr NA as compared to the oxocarbenium ion transition state analogue 2,3-dehydro-2-deoxy-N-acetylneuraminic acid. The sulfo-sialic acid analogues described in this report are also more potent inhibitors of influenza NA (up to 40-fold) and bacterial NA (up to 8.5-fold) relative to the corresponding anomeric phosphonic acids. These results confirm that this novel anomeric sulfo modification offers great potential to improve the potency of next-generation NA inhibitors including covalent inhibitors.

An efficient enantioselective total synthesis of EFdA, a remarkably potent anti-HIV nucleoside analogue with various favorable pharmacological profiles, has been achieved in 37% overall yield from diacetone-D-glucose by a 14-step sequence that features a highly diastereoselective installation of the tetrasubstituted stereogenic center at the C4' position, direct oxidative cleavage of an acetonide-protected diol derivative to an aldehyde, and one-pot 2'-deoxygenation of a ribonucleoside intermediate.

The influenza virus neuraminidase H274Y substitution is a highly prevalent amino acid substitution associated with resistance to the most heavily used influenza drug, oseltamivir. Previous structural studies suggest that the group specific 252 residue (Y252 in group 1 and T252 in group 2) might be a key factor underlying H274Y resistance. However, H274Y has only been reported in N1 subtypes, which indicates that there must be additional key residues that determine H274Y resistance. Furthermore, we found that members of NA serotype N3 also possess Y252, raising the key question as to whether or not H274Y resistance may also be possible for some group 2 NAs. Here, we demonstrate that the H274Y substitution results in mild oseltamivir resistance for N3. Comparative structural analysis of N3, N1, and their 274Y variants indicates that the interaction of residue 296 (H in N1 and nonaromatic for other serotypes) with conserved W295 is another important determinant of oseltamivir resistance.

EFdA (4'-ethynyl-2-fluoro-2'-deoxyadenosine), a nucleoside reverse transcriptase inhibitor with extremely potent anti-HIV activity, was concisely synthesized from (R)-glyceraldehyde acetonide in an 18% overall yield by a 12-step sequence involving highly diastereoselective ethynylation of an α-alkoxy ketone intermediate. The present synthesis is superior, both in overall yield and in the number of steps, to the previous one which required 18 steps from an expensive starting material and resulted in a modest overall yield of 2.5%.

A concise enantioselective total synthesis of 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA), an extremely potent anti-HIV agent, has been accomplished from (R)-glyceraldehyde acetonide in 18% overall yield by a 12-step sequence involving a highly diastereoselective ethynylation of an α-alkoxy ketone intermediate., (© 2011 American Chemical Society)

An idea to use 4'-C-substituted-2'-deoxynucleoside derivatives was proposed based on a working hypothesis to solve the problems of existing acquired immune deficiency syndrome chemotherapy (highly active antiretroviral therapy). Subsequent studies have successfully proved the validity of the idea and resulted in the development of 2'-deoxy-4'-C-ethynyl-2-fluoroadenosine and 2'-deoxy-4'-C-ethynyl-2-chloroadenosine, nucleoside reverse transcriptase inhibitors, which have supremely high activity against all human immunodeficiency viruses including multidrug-resistant HIV and low toxicity.

This article describes modified nucleosides with deactivated 3'-OH and modified at two or more positions. These are expected to have high antiviral activity as well as have low toxicity.

Bioassays of six racemic synthesized candidate sex pheromone compounds against male New World screwworm Cochliomyia hominivorax (Coquerel) flies showed that the most potent bioactivity was found with 6-acetoxy-19-methylnonacosane and 7-acetoxy-15-methylnonacosane compared with four other isomeric acetoxy nonacosanes and a larger aliphatic ketone. As all these methyl-branched compounds have two asymmetric carbons and four possible enantiomers, characterization of the natural enantiomers was essential. All four enantiomers for the two most bioactive isomers of the natural sex pheromone were synthesized for bioassay. Hydrolysis and derivatization of these enantiomers with different fluorescent reagents was followed by column-switched high-performance liquid chromatography. The use of two linked, reversed-phase columns of different polarity held at sub-ambient temperatures allowed good separation of each enantiomer. This analysis applied to natural material was successful, as (6R,19R)-6-acetoxy-19-methylnonanocosane, and (7R,15R)- and (7R,15S)-7-acetoxy-15-methylnonanocosane were detected in extracts of recently colonized female flies.

A new unsaturated fatty acid with unique vicinal dimethyl branches was isolated from the Okinawan soft coral of the genus Sinularia. The structure of the compound was determined based on the results of spectroscopic analysis and chemical conversion. The absolute configuration was deduced by applying the Ohrui-Akasaka method.

The development of highly potent chiral discrimination methods that solve the problems of the diastereomer method is described. Explaining the significant results of separations of diastereomers having chiral centers separated by 13 - 27 bonds with reversed-phase HPLC was hitherto impossible. To attract more scientific interest toward the mechanism of the separation, the author proposes a hypothesis, Induced Chiral Fields, that the achiral reversed phases can provide chiral fields depending on the structures of the substrates.

The structure of modified nucleosides expected to be highly anti-viral active and lowly toxic is proposed.

The development of highly potent chiral discrimination methods that solve the problems of the diastereomer method, in which it is impossible to discriminate the diastereomers having chiral centers separated by more than four bonds, is described. On the basis of the results obtained, a new hypothesis, Induced Chiral Fields that the achiral reversed phase can provide chiral fields depending on the structures of the eluents, is proposed to explain the significant results of separation of the diastereomers derived from newly developed chiral and fluorescent labeling reagents and optical isomers by reversed-phase HPLC, which was hitherto impossible.

2-(2,3-anthracenedicarboximido)cyclohexane derivatives (AC) have been known as the evolutionary diastereomerizing reagents for enantiomer discrimination in HPLC with ODS. However, a substantial separation of diastereomers can be observed only at lower temperatures, such as -40 degrees C. Therefore, in this work, poly(octadecyl acrylate)-grafted silica, ODAn was applied as an alternative stationary phase to ODS for the separation of AC-derived diastereomers. As a result, complete separation was achieved even under the conventional condition: for example, methanol as the mobile phase and 0 degrees C as the column temperature. An investigation on the temperature dependency of the selectivity demonstrated that ODAn shows a remarkable increase in selectivity at temperatures below 30 degrees C, which almost agreed with the peak-top temperature of the endothermic peak in a DSC thermogram for ODA35 immersed in a mobile phase. The better separation would be derived from a highly ordered structure of ODAn and a carbonyl-pi interaction with AC-derived diastereomers.

Working hypotheses to solve the critical problems of the existing highly active anti-retroviral therapy were proposed. The study based on the hypotheses proved the validity of the hypotheses and resulted in the development of 2'-deoxy-4'-C-ethynyl-2-fluoroadenosine, a nucleoside reverse transcriptase inhibitor, with highly potent activity against all HIV-1, very favorable toxic profiles, and stability in plasma. The nucleoside will prevent or delay the emergence of drug-resistant HIV-1 variants and be an ideal therapeutic agent for both HIV-1 and HBV infections.

Enantiomeric discrimination of chiral primary amines was performed by both reversed-phase HPLC and normal-phase HPLC after labeling with a chiral fluorescent derivatization reagent, (1R,2R)- and (1S,2S)-trans-2-(2,3-anthracenedicarboximido)cyclohexanecarbonyl chloride. Use of HPLC permits separation of diastereomeric derivatives of amines up to C30 which have a primary amino group at the middle of the alkyl chain. The derivatives of primary amines having an anteiso alkyl chain, which has a chiral branched-methyl at the n-3 position of the alkyl chain, were also separated by HPLC, and it was also possible to separate niphatesine D by reversed-phase HPLC after derivatization.

The chemiluminescence of gallic acid by hydrogen peroxide had completely inhibited by the presence of ascorbate. After ascorbate had disappeared by oxidation, chemiluminescence returned. The concentration of gallic acid was virtually unchanged by presence of ascorbate, but started to decrease after the disappearance of ascorbate. This might be attributable to the rapid reduction of quinone, which was the first product of the chemiluminescence reactions, to gallic acid by ascorbate or the donation of proton to the phenoxy radical from ascorbate to stop the chemiluminescence reaction at the first stage. The effects of ascorbate on the chemiluminescence of other polyphenols depended on their oxidation rate.

An idea to use 4'-C-substituted-2'-deoxynucleoside derivatives was proposed based on a working hypothesis to solve the problems of existing acquired immune deficiency syndrome chemotherapy (highly active antiretroviral therapy). Subsequent studies have successfully proved the validity of the idea and resulted in the development of 2'-deoxy-4'-C-ethynyl-2-fluoroadenosine, a nucleoside reverse transcriptase inhibitor, which is highly potent to all human immunodeficiency viruses type 1 (HIV-1s) including multidrug-resistant HIV-1 and has a low toxicity.

A working hypothesis to solve the critical problems of existing HAART was proposed. The study based on the hypothesis proved the validity of the hypothesis and resulted in the development of 2'-deoxy-4'-C-ethynyl-2-fluoro-adenosine (4'Ed2FA), a nucleoside reverse transcriptase inhibitor (NRTI) with highly potent activity against all HIV-1 strains, very favourable toxic profiles, and stability in plasma.

A diastereomeric mixture and the four stereoisomers of 2,6-dimethyloctane-1,8-dioic acid (2), a copulation release pheromone of the cowpea weevil, Callosobruchus maculatus, were synthesized. The stereoisomeric purities of the four synthetic isomers of 2 were determined by the HPLC analyses of their bis-2-(2,3-anthracenedicarboximide)-1-cyclohexyl esters.

The crystalline structure of N-(S)-2-heptyl (1R,2R)-2-(2,3-anthracenedicarboximido)cyclohexamide (1), which was crystallized from methanol, was determined by an X-ray analysis and had a different conformation from its preferred one in CD3OD by a 1H-NMR analysis. Inter- and intra-molecular CH-pi interaction in a crystal plays a very important role in crystal packing. The preferred conformation of the amide derivative in a solution allows us to exploit (1R,2R)-2-(2,3-anthracenedicarboximido)cyclohexanecarbonyl chloride as a conversion reagent to determine the absolute configuration of chiral amines by 1H-NMR.

We synthesized new chiral fluorescence labeling reagents having a 2,3-anthracenedicarboximide group from D-glucosamine, and it was possible to introduce target alcohols at the anomeric positions of the reagents with beta-selectivity by glycosidations. Especially, it was possible to use methyl glycoside reagent as a glycosyl donor with a Lewis acid and microwave irradiation, and it gave selectively beta-glycoside while the reaction without microwave irradiation gave alpha- and beta-mixed glycosides. Those reagents showed very high chiral discrimination ability, and they made it possible to separate the eight stereoisomers of 4,8,12,16-tetramethylheptadecanol by HPLC after derivatizations.

Enantiomeric discrimination of chiral secondary alcohols was performed by both reversed-phase HPLC and 1H-NMR after labeling with a chiral fluorescent derivatization reagent, 2-(2,3-anthracenedicarboximide)cyclohexanecarboxylic acid. It was possible to discriminate by HPLC the chirality of alcohols up to C30 having a chiral hydroxyl group at the middle of the straight alkyl chain, and, by 1H-NMR, alcohols up to C16. For alcohols having one straight alkyl and one isoalkyl group with the same carbon numbers at both sides of a hydroxyl group, it was possible to discriminate the chiralities of alcohols up to C19 by both 1H-NMR and HPLC. The 1H-NMR methods also made it possible to determine absolute configurations empirically., (2004 Wiley-Liss, Inc.)

The four stereoisomers of 7-acetoxy-15-methylnonacosane (1), a component of the female sex pheromone of the New World screwworm fly (Cochliomyia hominivorax) were synthesized. The stereogenic center at C-15 of 1 originated from that of the enantiomers of citronellal, and that at C-7 was generated by lipase-catalyzed asymmetric acetylation of (3RS,11R)- and (3RS,11S)-17-methyl-1-trimethylsilylpentacos-1-yn-3-ol (13). Three of the stereoisomers of 1 showed equivalent good pheromone activity, while the activity of (7R,15R)-1 was weak.

Extensive efforts have been made to identify nucleoside reverse transcriptase inhibitors (NRTIs). Eight NRTIs have now been approved for clinical use; however, variants of HIV-1 resistant to these antiviral agents have emerged in patients even when they are treated with combinations [highly active antiretroviral therapy (HAART)]. Thus, the development of novel compounds that are active against drug-resistant HIV-1 variants and that prevent or delay the emergence of resistant HIV-1 variants is urgently needed. Previously, 4'-C-substituted nucleosides (4'-SNs) were designed as new types of NRTIs. They were synthesized and examined as potential therapeutic agents against HIV infection. Among them, several 4'-substituted-2'-deoxynucleosides (4'-SdNs), especially those that bear an ethynyl group, were shown to be active against various laboratory and clinical HIV-1 strains including known drug-resistant variants. These results were recently reported by our collaborators. In this review, we summarize the design, synthesis and demonstrations of the anti-HIV activity of 4'-SNs, and then consider 4'-SNs as potential therapeutic agents for HIV-1.

The nonmevalonate pathway is widely found in higher plants and in many eubacteria, including pathogenic ones, but not in mammals. Identifying a nonmevalonate pathway inhibitor would greatly contribute to the search for new herbicides and antibacterial drugs to treat, for example, malaria. We describe here the synthesis of (3R,4S)-3,4,5-trihydroxy-4-methylpentylphosphonic acid as a candidate for inhibiting MEP cytidylyltransferase, which is the third step on the nonmevalonate pathway.

We investigated the potential of 4'-C-substituted nucleosides for the treatment of HIV-1 and HBV. Of the nucleosides we prepared, several 4'-C-ethynyl-2'-deoxypurine nucleosides showed the most potent anti-HIV activity. However, two candidates, 4'-C-ethynyl-2'-deoxyguanosine and 9-(2-deoxy-4-C-ethynyl-beta-D-ribo-pentofuranosyl)-2,6-diaminopurine, were very toxic during in vivo study. On the other hand, lamivudine (3TC) is known to show remarkable activity against HIV and HBV with lower cytotoxicity. Therefore, we attempted to synthesize the L-enantiomer of 4'-C-ethynyl-2'-deoxypurine nucleosides in 20-21 steps. These methods consisted of preparing 4-C-ethynyl-L-sugar, starting from D-arabinose and then condensing the L-sugar derivative with 2,6-diaminopurine. 4'-C-Ethynyl-2'-deoxyguanosine was also prepared by enzymatic deamination from the 2,6-diaminopurine derivative. The compounds' antiviral activity against HIV and HBV was then evaluated. Unfortunately, they demonstrated no activity and no cytotoxicity.

Some 4'-C-ethynyl-2'-deoxy purine nucleosides showed the most potent anti-HIV activity among the series of 4'-C-substituted 2'-deoxynucleosides whose 4'-C-substituents were methyl, ethyl, ethynyl and so on. Our hypothesis is that the smaller the substituent at the C-4' position they have, the more acceptable biological activity they show. Thus, 4'-C-cyano-2'-deoxy purine nucleosides, whose substituent is smaller than the ethynyl group, will have more potent antiviral activity. To prove our hypothesis, we planned to develop an efficient synthesis of 4'-C-cyano-2'-deoxy purine nucleosides (4'-CNdNs) and 4'-C-ethynyl-2'-deoxy purine nucleosides (4'-EdNs). Consequently, we succeeded in developing an efficient synthesis of six 2'-deoxy purine nucleosides bearing either a cyano or an ethynyl group at the C-4' position of the sugar moiety from 2'-deoxyadenosine and 2,6-diaminopurine 2'-deoxyriboside. Unfortunately, 4'-C-cyano derivatives showed lower activity against HIV-1, and two 4'-C-ethynyl derivatives suggested high toxicity in vivo.

Anteiso fatty acids having 16 to 29 carbon atoms were labeled with the chiral fluorescent conversion reagents, (1R,2R)- and (1S,2S)-2-(2,3-anthracenedicarboximido)cyclohexanol. The diastereomeric esters of anteiso acids having up to 20 carbon atoms were separated into two peaks in an ODS column under low column-temperature conditions, while those having more than 21 carbon atoms were not separated. A C30 column made it possible to separate diastereomeric esters up to C29 anteiso acid. It was possible to predict the absolute configuration of each acid by the elution order of the derivatives.

Highly sensitive chiral labeling reagents, (1R,2R)- and (1S,2S)-2-(2,3-anthracenedicarboximido)cyclohexanecarboxylic acids [(1R,2R)- and (1S,2S)-A] and (1R,2R)- and (1S,2S)-2-(2,3-naphthalenedicarboximido)cyclohexanecarboxylic acids [(1R,2R)- and (1S,2S)-A'], were prepared. Reagent A has enabled us to discriminate the enantiomers of anteiso fatty alcohols up to C9 methyl branching by 1H NMR, and both reagents A and A' have allowed up to C16 methyl branching at the 10(-15) molar level by fluorescence detected reversed-phase HPLC.

Purine 2'-deoxynucleosides bearing an ethynyl or a cyano group at C-4' of the sugar moiety were synthesized from the corresponding 2'-deoxynucleosides. These compounds exhibited very potent anti-HIV activity, and remained active against drug resistant HIV strains.

The absolute configurations of the two acid moieties, 12-methyltetradecanoate and 14-methylhexadecanoate, of glycoglycerolipid S365A isolated from Corynebacterium aquaticum were determined by an HPLC analysis after their conversion with the chiral fluorescent labeling reagents, (1S,2S)- and (1R,2R)-2-(2,3-anthracenedicarboximido)cyclohexanol. Both anteiso acids had the S configuration.

The L-enantiomer of 4'-C-ethynyl-2'-deoxycytidine (2) was synthesized, but did not show any activity against HIV-1 up to 100 microM.

Molecular design and applications of a fluorometric chiral agent, (S)-TBMB carboxylic acid, are briefly reviewed. The agent, possessing an asymmetric 1,3-benzodioxole skeleton, was designed as a novel class of chiral agent that functions also as a benzoate chromophore for exciton chirality CD methods. The utility of this agent has been demonstrated in an application to determine enantiomeric amino acids, acyl-sn-glycerols, glycosyl-sn-glycerols, and other chiral alcohols and amines., (Copyright 2001 Wiley-Liss, Inc.)

A series of 4'-ethynyl (4'-E) nucleoside analogs were designed, synthesized, and identified as being active against a wide spectrum of human immunodeficiency viruses (HIV), including a variety of laboratory strains of HIV-1, HIV-2, and primary clinical HIV-1 isolates. Among such analogs examined, 4'-E-2'-deoxycytidine (4'-E-dC), 4'-E-2'-deoxyadenosine (4'-E-dA), 4'-E-2'-deoxyribofuranosyl-2,6-diaminopurine, and 4'-E-2'-deoxyguanosine were the most potent and blocked HIV-1 replication with 50% effective concentrations ranging from 0.0003 to 0.01 microM in vitro with favorable cellular toxicity profiles (selectivity indices ranging 458 to 2,600). These 4'-E analogs also suppressed replication of various drug-resistant HIV-1 clones, including HIV-1(M41L/T215Y), HIV-1(K65R), HIV-1(L74V), HIV-1(M41L/T69S-S-G/T215Y), and HIV-1(A62V/V75I/F77L/F116Y/Q151M). Moreover, these analogs inhibited the replication of multidrug-resistant clinical HIV-1 strains carrying a variety of drug resistance-related amino acid substitutions isolated from HIV-1-infected individuals for whom 10 or 11 different anti-HIV-1 agents had failed. The 4'-E analogs also blocked the replication of a non-nucleoside reverse transcriptase inhibitor-resistant clone, HIV-1(Y181C), and showed an HIV-1 inhibition profile similar to that of zidovudine in time-of-drug-addition assays. The antiviral activity of 4'-E-thymidine and 4'-E-dC was blocked by the addition of thymidine and 2'-deoxycytidine, respectively, while that of 4'-E-dA was not affected by 2'-deoxyadenosine, similar to the antiviral activity reversion feature of 2',3'-dideoxynucleosides, strongly suggesting that 4'-E analogs belong to the family of nucleoside reverse transcriptase inhibitors. Further development of 4'-E analogs as potential therapeutics for infection with multidrug-resistant HIV-1 is warranted.

In the past years, a variety of 4'-C-substituted-2'-deoxynucleosides (4'SdNs) were designed, synthesized, and examined as potential therapeutics against human immunodeficiency virus (HIV) infection and certain such analogues proved to exert potent activity against HIV-1 in vitro. Unlike currently available nucleoside reverse transcriptase (RT) inhibitors such as 3'-azido-3'-deoxythymidine (AZT), which have the 2',3'-dideoxy configuration and thereby cause DNA chain termination in the elongating proviral DNA, 4'SdNs do retain the 3'-alpha-OH moiety but also appear to work against retrovirus as proviral DNA chain terminators. Several 4'SdNs have been shown to be active against various laboratory and clinical HIV-1 strains including known drug-resistant HIV-1 variants. Among such 4'SdNs is 4'-azido-2'-deoxythymidine (4'-AZT) which exerts potent antiviral activity against wild type and AZT-resistant clinical HIV strains. More anti-HIV 4'SdNs have recently been reported including 4'-ethynylthymidine, 4'-ethynyl-2'-deoxy-D-ribofuranosyl-2,6-diaminopurine (4'-E-dDAP), 4'-ethynyl-2'-deoxyguanosine (4'-E-dG) and 4'-ethynyl-2'-deoxyadenosine (4'-E-dA). The latter three analogues are highly potent against HIV-1 and HIV-2 with EC50 values ranging from 0.0003 to 0.01 microM and have favorable cytotoxicity profiles with selective index (SI) values ranging from 975 to 2600. These 4'-ethynyl-2'-deoxynucleosides also exert potent activity against all known drug-resistant HIV-1 variants including the multi-dideoxynucleoside-resistant HIV and the variants with the 6-base pair inserts. Some of these compounds have favorable pharmacological properties and further development as potential therapeutics against HIV-1 infection is warranted.

4'-C-Ethynyl-beta-D-arabino- and 4'-C-ethynyl-2'-deoxy-beta-D-ribo-pentofuranosylpyrimidine and -purine nucleosides were synthesized and evaluated for their in vitro anti-HIV activity. The key intermediate, 4-C-ethynyl- or 4-C-triethylsilylethynyl-D-ribo-pentofuranose, was prepared from D-glucose and glycosidated with various pyrimidine or purine bases. The arabinopyrimidine derivatives were prepared from the corresponding ribo derivatives via O(2),2'-anhydro nucleosides. The 2'-deoxy-ribo derivatives were synthesized by radical reduction of 2'-bromo or 2'- phenoxythiocarbonyloxy nucleosides. Among these 4'-C-ethynyl nucleosides, seven analogues proved to be potent against HIV-1 in vitro with EC(50) values ranging from 0.0003 to 0. 03 microM. These compounds also exerted activity against clinical and multi-dideoxy-nucleoside-resistant HIV-1 strains with comparable EC(50) values. Three such 4'-C-ethynyl-2'-deoxypurine analogues including 4'-C-ethynyl-2'-deoxyadenosine and 4'-C-ethynyl-2, 6-diamino-2'-deoxypurine were less cytotoxic [selectivity indices (SIs): 975-2733] than three 4'-C-ethynyl-2'-deoxycytidine analogues (SIs: 63-363). 4'-C-Ethynyl-5-fluoro-2'-deoxycytidine was least toxic (SI: >3333) and potent against all HIV strains tested.

D-Galactosyl-alpha-1,3-D-galactopyranose (1) was chemically prepared in a good yield by coupling phenyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-galactopyranoside (5) or 2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl bromide (8) with 1,2:5,6-di-O-cyclohexylidene-alpha-D-galactofuranose (3) with subsequent de-O-benzylation and de-O-cyclohexylidenation of the resulting protected alpha1,3-disaccharide.

2-C-Methyl-D-erythritol (A) and 2-C-methyl-L-threitol (B) were respectively synthesized from D-glucose and D-galactose. The 2-C-methyl-1,2,3,4-butanetetrol compound (C) recently isolated from Phlox sublata L was confirmed to be A by comparing the CD and 1H-NMR spectra of its tri-O-benzoate with those of A and B.

The absolute configuration of the chiral center at the C15 position of a novel branched-chain fatty acid derived from a new ceramide isolated from the epiphytic dinoflagellate Coolia monotis was determined to be of R from by reversed-phase HPLC after cleavage to 12-methylpentadecanoic acid and subsequent conversion with the chiral fluorescent reagent, (1R,2R)-2-(2,3-anthracenedicarboximido)cyclohexanol.

Phosphine reagents were designed and synthesized as a new type of fluorescent reagents for the determination of lipid hydroperoxides in foodstuff and biological materials. All phosphine reagents prepared had no fluorescence but their oxides, which were produced by the reaction of the phosphines with hydroperoxides, had strong fluorescence. Among the phosphine reagents prepared, diphenyl-1-pyrenylphosphine had the most suitable properties as a fluorescent reagent and was successfully applied to the determination of hydroperoxides by batch, flow injection and HPLC post-column methods.

Searching for more effective anti-HIV agents, we have prepared 4'-ethynyl-purine nucleosides. They were derived in several steps from 4-C-triethylsilylethynyl ribose, which was used as an intermediate in the synthesis of pyrimidine nucleosides. The adenine derivative exhibited significant anti-HIV activity and favorable cytotoxicity profile in vitro.

4'-C-Ethynyl-beta-D-arabino-pentofuranosyl thymine (14) and cytosine (16), and 4'-C-ethynyl-2'-deoxy-beta-D-ribo-pentofuranosyl thymine (25) and cytosine (27) were synthesized by properly protected 4'-C-hydroxy-methyl-3,5-di-O-benzyl-alpha-D-ribo-pentofuranose (1) from D-glucose. Among them, 2'-deoxy derivatives 25 and 27 exhibited antiviral activity, while cytidine derivatives 16 and 27 inhibited the growth of neoplastic cells.

Two novel 4'-C-methylnucleosides, 4'-methylBVDU 9 and 4'-methylBVaraU 10, were synthesized. The former was derived from 3',5'-di-O-acetyl-2'-deoxy-4'-C-methyluridine 12, and the latter was produced via glycosylation between 4-C-methyl-D-ribose derivative 11 and a silylated bromovinyl uracil. 4'-MethylBVDU 9 exhibited particularly potent anti-varicella-zoster virus (VZV) activity in vitro.

(1R,2R)-2-(2,3-Anthracenedicarboximido)cyclohexanol was synthesized as a highly sensitive chiral fluorescent conversion reagent. The diastereomeric derivatives of chiral branched fatty acids that had methyl ethyl chirality from the 2 to 12 position were separated into 2 peaks by reversed-phase HPLC and detected at the 10(-15) mole level by fluorometry.

4'-C-Ethynyl-beta-D-arabino- and 4'-C-ethynyl-beta-D-2'-deoxy-ribo-pentofuranosyl pyrimidines were synthesized. Most of these 4'-ethynyl nucleosides showed interesting biological activities.