Krystyna Lesiak

AIDS dementia: Synthesis and properties of a derivative of 3′‐azido‐3′‐deoxythymidine (AZT) that may become ‘locked’ in the central nervous system

In an attempt to provide a derivative of 3′‐azido‐3′‐deoxythymidine (AZT) which might be sequestered in the central nervous system and release AZT, the dihydropyridine ester 5′‐(1,4‐dihydro‐1‐methyl‐3‐pyridinylcarbonyl)‐3′‐deoxythymidine, was synthesized in a three step sequence. This material showed potent anti‐HIV‐1 activity in MT‐4 cells most probably by hydrolysis to the parent nucleoside, AZT. This dihydropyridine derivative of AZT could be easily oxidized to a positively charged pyridinium derivative of AZT in rat brain cytosol. In turn the pyridinium form could be hydrolyzed, non‐enzymatically, to AZT.

The solid-phase synthesis of 2'-5'-linked oligoriboadenylates containing 8-bromoadenine

To increase the accessibility of 8-bromo-2′,5′-oligoadenylates, we developed a synthesis of 2′-5′-linked oligoriboadenylates containing varying numbers of 8-bromoadenosine residues based on the use of a CPG-LCA solid support and the phosphoramidite approach. Although N6benzoyl protection was satisfactory for incorporation of nonmodified adenine residues into 2′,5′-oligonucleotides, the effective incorporation of 8-bromoadenine into such 2′,5′-linked oligomers required use of a non acyl protecting group. Amidine protection of the purine exocyclic amino function proved compatible with all aspects of the phophoramidite approach and with the hydroxyl protection groups employed.

TARGETING RNA FOR DEGRADATION WITH A (2',5')-OLIGOADENYLATE ANTISENSE CHIMERA

Abstract A novel method is described to selectively cleave RNA by harnessing the 2-5A-dependent ribonuclease.

Synthesis and biological activity of a fluorescent analogue of 2—5A

A fluorescent analogue of 2—5A, ppp5′ ϵA2′p5′ϵA2′p5′ϵA, was obtained by reaction of 2′, 5′ (pA)3 with chloroacetaldehyde followed by conversion to the 5‐triphosphate through reaction of the corresponding phosphoroimidazolide with pyrophosphate anion. The 5′‐monophosphate, p5′ϵA2′p5′ϵA2′p5′ϵA, was not an antagonist of 2—5A action in extracts of mouse L cells. Neither did the 5′‐triphosphate, ppp5′ϵA2′p5′ϵA2′p5′ϵA, inhibit translation. Moreover, the 5′‐triphosphate was bound to the 2—5A‐dependent endonuclease 5000‐times less effectively than 2—5A itself.

A Solid-Phase Synthesis of 2′,5′-Linked Oligoadenylates (2-5A)

Abstract 2′,5′-Oligoadenylate 5′-triphosphates (2-5A) as products of 2-5A synthetase and activators of ribonuclease L (RNase L), are mediators in one of the mechanisms of interferon′s antiviral action. Upon activation, RNase L inhibits protein synthesis due to the degradation of RNAs. This activity of 2-5A could possibly find an application in virus or cancer chemotherapy, but two major barriers prevent the use of 2′,5′-linked oligoadenylates as therapeutic agents. The 2-5A is readily degraded by a 2′,5′ phosphodiesterase and as a highly negatively charged molecule, is not readily taken up by cells. One possible solution to this latter limitation might be found in chemical modifications of the 2-5A structure. Many analogues of 2-5A have been already obtained with modified base, ribose or phosphate moieties. While these have provided some important information about the enzyme- activator interactions, the cell permeability problem still remains unsolved. One of the major obstacles in this study is lack of ...

Strategies in the Design of Oligonucleotides as Potential Antiviral Agents

Polynucleotides have enjoyed considerable success as antiviral or antitumor agents due to their interferon-inducing ability1,2, their immunoadjuvant activity3, their reverse-transcriptase inhibitor properties4 or their capacity to inhibit virion-associated transcriptases5. On the other hand, the small sequence-defined oligonucleotides, until recently, have attracted little interest in this regard. Nonetheless, the potential of oligonucleotides as chemotherapeutic agents has been long appreciated. Levene and Stollar6 obtained partial inhibition of systemic lupus erythematosus sera by tetra- and pentanucleotides, and Shen7 suggested the design of high affinity oligonucleotide inhibitors of antigen-antibody complex formation. Oligonucleotides also have been employed as prodrug forms8, but we will not deal with this particular application.

Synthesis of 2′-Deoxynucleoside 5′-Methylenebis-(phosphonate)s Using 2-(4-Nitrophenyl)ethyl Methylenebis(phosphonate) as the Phosphonylating Agent.

Abstract 2-(4-Nitrophenylethyl) methylenebis(phosphonate) (1) has been prepared by reaction of 2-(4-nitrophenyl)ethyl alcohol with methylenebis(phosphonyl) tetrachloride. Compound 1 was treated with diisopropylcarbodiimide (DIC) to give bicyclic intermediate 2, which in reaction with suitably protected 2′-deoxynucleosides 3 gave P1,P2-disubstituted methylenebis(phosphonate)s 4. Removal of the nitrophenylethyl group by β-elimination with DBU afforded the corresponding 2′-deoxynucleoside 5′-methylenebis(phosphonate) analogues 5. This paper is dedicated to the 60th birthday of Professor Jacques H. van Boom.

Adducts of Mannose 6-Phosphate with 5-Iodo-2′-Deoxyuridine and 2-5A as Potential Antiviral Agents

Abstract To examine the possibility that the mannose 6-phosphate receptor system might be capitalized upon to facilitate uptake of nucleotides or nucleotides into cell, adducts of mannose 6-phosphate with 5-iodo-2′-deoxyuridine 5′-monophosphate and with adenosine 5′-monophosphate, p5′A2′p5′A and p5′A2′p5′A2′p5′A were prepared and evaluated for their antiviral activities. The adducts with 2′,5′-oligoadenylates possessed no significant antiviral activity. The adduct with 5-iodo-2′-deoxyuridine 5′-monophosphate showed activity that could be fully explained by extracellular cleavage to free 5-iodo-2′-deoxyuridine.

Modes of action of interferon and analogues of 2-5A, a mediator of interferon action

In the last few years, several different interferons have been described, cloned, sequenced, expressed in heterologous systems and purified to homogeneity (Weissmann et al., 1982; Kingsman & Kingsman, 1983). In particular for human interferons there exists at least thirteen subtypes of IFN-α, one IFN-β and one IFN-γ. All these molecular species and some of their recombinant hybrids show a number of common biological properties but also distinctive antiviral (Weck et al., 1981; Kingsman & Kingsman, 1983) and other activities (Rehberg et al., 1982; Pestka et al., 1983b). Recombinant DNA technology has substantially contributed to the study of the mechanism of action of interferon and will probably continue to do so in the future by allowing a detailed analysis of the regulation and site-directed mutagenesis of IFN-induced proteins.

SYNTHESIS OF METHYLENEBIS(PHOSPHONATE) ANALOGUES OF NUCLEOTIDE COENZYMES. A NOVEL COUPLING MECHANISM

Synthesis of P1, P2-disubstituted methylenebis(phosphonate)s as inhibitors of inosine monophosphate dehydrogenase is presented.