Cristina Chamorro

Regio- and enantioselectivity of the Candida antarctica lipase catalyzed amidations of Cbz-l- and Cbz-d-glutamic acid diesters

Abstract Candida antarctica lipase (CAL) catalyzed amidation of Cbz-glutamic acid diesters takes place in a regioselective way to give the corresponding monoamide derivatives. The regioselectivity was found to be dependent on the reacting Glu enantiomer. Thus, amidations of Cbz- l -Glu diesters regiospecifically afforded α-amide while the γ-ester is selectively substituted in the d -enantiomer. This enzymatic reaction also shows enantioselectivity when a chiral amine is used as nucleophile.

Hiv-1 Specific Reverse Transcriptase Inhibitors: why are Tsao-Nucleosides so Unique?

1. INTRODUCTION AIDS will still be one of the most important challenges for the Scientific Community in the approaching new century. Since the identification, in 1983-84,1,2 of human immunodeficiency virus (HIV) as the etiological agent of AIDS, significant progress has been made in the treatment of HIV-infected patients. This has been in part due to the discovery and clinical use of an increasing number of anti-HIV drugs. However, while highly active antiretroviral therapy (HAART)3 approaches have reduced the morbidity and mortality, the intertwined problems of drug induced viral resistance, poor compliance with complex regimens and therapy failure continue. Therefore, there remains a pressing need for the development of new antiviral agents that can be used not only as first line therapeutic candidates, but also in the antiretroviral-experienced patient population.

TSAO-T analogues bearing amino acids at position N-3 of thymine: synthesis and anti-human immunodeficiency virus activity.

Novel analogues of the anti-HIV-1 lead compound [1-[2‘,5’-bis-O-(tert-butyldimethylsilyl)-β-D-ribofuranosyl]thymine]-3‘-spiro-5’-(4“-amino-1”,2“-oxathiole-2‘,2’-dioxide) (TSAO-T) bearing different amino acids at position N-3 of thymine were prepared and evaluated as inhibitors of HIV replication. The synthesis of the target compounds was accomplished by coupling of the appropriate TSAO intermediate with a conveniently protected (L) amino acid in the presence of BOP and triethylamine, followed by depro-tection of the amino acid moiety. Several TSAO derivatives, bearing at N-3 position of the thymine base an L-amino acid retaining the free carboxylic acid, acquired activity against HIV-2, in addition to their inhibitory effect on HIV-1.

Novel Series of [ddN]-[TSAO-T] Heterodimers as Potential Bi-Functional Inhibitors of HIV-1 RT. Studies in the Linker and ddN Region

Novel series of [ddN]-(CH2)n-[TSAO-T] heterodimers have been prepared and tested for their anti-HIV-1 and HIV-2 activity. The most active compound of this series was the [d4T]-(CH2)3-[TSAO-T] heterodimer (EC50 = 0.018 +/- 0.03 microM).

N-3 Substituted TSAO Derivatives as a Probe to Explore the Dimeric Interface of HIV-1 Reverse Transcriptase

Reverse transcriptases (RTs) from both human immunodeficiency viruses type 1 (HIV-1) and 2 (HIV-2) are obligatory dimers and only dimeric forms of this enzyme are actives. It has been suggested that the dimerization of RT might be a good target for therapeutic intervention in AIDS. TSAO-T bearing at N-3 an ethyl moiety (TSAO-eT) belongs to a unique family of HIV-1-specific non-nucleoside RT inhibitors (NNRTIs). It is the only small molecule that has been shown to interfere with the HIV-1 RT dimerization process by destabilizing the p66=p51 and p66=p66 dimeric forms of HIV-1 RT. Recently, we have reported a model of interaction of TSAO derivatives with the HIV-1 RT. In this model, TSAO straddles between the subunits at the p66=p51 interface. The N3 substituents of the thymine base of the TSAO compounds are positioned parallel to the subunit interface.

Synthesis of Novel 5″-Substituted Tsao-T Analogues with Anti-Hiv-1 Activity

INTRODUCTION TSAO derivatives are potent and selective HIV-1 reverse transcriptase (HIV-1 RT) inhibitors. Although, structurally, they can be considered as highly functionalized nucleosides, they inhibit their target enzyme (HIV-1 RT) similarly to the so-called Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTI).1-6 The different families of NNRTI, including TSAO, interact with the HIV-1 RT in a highly hydrophobic pocket, close but different from the active site, and several complexes of NNRTIs-HIV-1 RT have been resolved by X-ray crystallography.7-15

An approach towards the synthesis of potential metal-chelating TSAO-T derivatives as bidentate inhibitors of human immunodeficiency virus type 1 reverse transcriptase

Novel derivatives of the potent human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) inhibitor TSAO-T have been designed, synthesized and tested for their in vitro antiretro-viral activity against HIV. These TSAO-T derivatives have been designed as potential bidentate inhibitors of HIV-1 RT, which combine in their structure the functionality of a non-nucleoside RT inhibitor (TSAO-T) and a bivalent ion-chelating moiety (a β-diketone moiety) linked through an appropriate spacer to the N-3 of thymine of TSAO-T . Some of the new compounds have an anti-HIV-1 activity comparable to that of the parent compound TSAO-T, but display a markedly increased antiviral selectivity. There was a clear relationship between antiviral activity and the length of the spacer group that links the TSAO molecule with the chelating moiety. A shorter spacer invariably resulted in increased antiviral potency. None of the TSAO-T derivatives were endowed with anti-HIV-2 activity.

Structure-activity relationship studies on a novel family of specific HIV-1 reverse transcriptase inhibitors.

We have previously reported the discovery and preliminary structure-activity relationships of a new class of specific HIV-1 reverse transcriptase (RT) inhibitors whose prototype compound is the 1-[2′,5′-bis-O-(tert-butyldimethylsilyl)-β-D-ribofuranosyl]-3-N-[(carboxy) methyl]-thymine. In an attempt to increase the inhibitory efficacy against HIV-1 RT of this new class of nucleosides, and to further explore the structural features required for anti-HIV-1 activity, different types of modifications have been carried out on the prototype compound. These include substitution of the tert-butyldimethylsilyl groups by other liphophilic groups, replacement of the carboxy group at the N-3 position of the nucleobase by other functional groups, change in the length of the spacer between the thymine and the carboxylic acid residue and substitution of the thymine moiety by other pyrimidine (uracil, 5-ethyluracil) or purine (hypoxanthine) nucleobases. In addition, the most salient structural features of this new class of HIV-1-specific nucleosides have been incorporated into classical HIV RT nucleoside inhibitors such as ddI, AZT, d4T. Our studies demonstrate that both the carboxymethyl moiety at the nucleobase and tert-butyldimethylsilyl groups at the sugar are important structural components since deletion of either of them is detrimental to the antiviral activity.

Identification of a novel family of nucleosides that specifically inhibit HIV-1 reverse transcriptase

N-3-Benzyloxycarbonylmethyl- and N-3-carboxymethyl-TBDMS-substituted nucleosides were synthesized and evaluated for activity against HIV replication. It was found that the N-3-carboxymethyl-TBDMS-substituted nucleosides were specific inhibitors of HIV-1 replication. They should be considered as members of a novel and original class of NNRTIs.

UNEXPECTED RESULTS IN THE REACTION OF 5'-TOSYL TSAO-M3T WITH AMINES

Abstract We report our strategies to prepare TSAO compounds carrying at 5′-position groups, such as amines, that may be positively charged at physiological conditions, unexpectedly, cyclic TSAO-derivatives were obtained. A possible mechanism for the formation of these unexpected compounds is advanced.