Yahya El-Kattan

A GENERAL SYNTHETIC METHOD OF 5-CARBORANYLURACIL NUCLEOSIDES WITH POTENTIAL ANTIVIRAL ACTIVITY AND USE IN NEUTRON CAPTURE THERAPY

Abstract Previous biochemical and pharmacological studies indicated that 5-o-carboranyl-2′-deoxyuridine is a lead candidate for boron neutron capture therapy. This prompted the development of a rapid and stereoselective N 1-glycosylation reaction of silylated 5-o-carboranyluracil with a variety of protected sugars. The key intermediate, 5-o-carboranyluracil (6), was prepared from 5-iodouracil in six steps. A novel coupling procedure of the 2,4-dimethoxy-5-ethynylpyrimidine (4) with decaborane without activator was used. Silylated 6 was coupled with a variety of carbohydrates under mild conditions to produce several carborane containing nucleosides. In each case, the stereochemistry and stereoselectivity of the glycosylation reaction was not affected by the presence of the carborane at the 5-position of the uracil and produced exclusively closo [closo-1,2-C2B10H12 cage] nucleosides. This was confirmed by X-ray structure determination of racemic 5-carboranyl-2′,3′-dideoxy-3′-thiauridine. This compound demon...

Design, parallel synthesis, and crystal structures of biphenyl antithrombotics as selective inhibitors of tissue factor FVIIa complex. Part 1: Exploration of S2 pocket pharmacophores

Factor VIIa (FVIIa), a serine protease enzyme, coupled with tissue factor (TF) plays an important role in a number of thrombosis-related disorders. Inhibition of TF x FVIIa occurs early in the coagulation cascade and might provide some safety advantages over other related enzymes. We report here a novel series of substituted biphenyl derivatives that are highly potent and selective TF x FVIIa inhibitors. Parallel synthesis coupled with structure-based drug design allowed us to explore the S2 pocket of the enzyme active site. A number of compounds with IC(50) value of <10 nM were synthesized. The X-ray crystal structures of some of these compounds complexed with TF x FVIIa were determined and results were applied to design the next round of inhibitors. All the potent inhibitors were tested for inhibition against a panel of related enzymes and selectivity of 17,600 over thrombin, 450 over trypsin, 685 over FXa, and 76 over plasmin was achieved. Two groups, vinyl 36b and 2-furan 36ab, were identified as the optimum binding substituents on the phenyl ring in the S2 pocket. Compounds with these two substituents are the most potent compounds in this series with good selectivity over related serine proteases. These compounds will be further explored for structure-activity relationship.

An Efficient Synthesis Of Acyclic N7- and N9-Adenine Nucleosides Via Alkylation With Secondary Carbon Electrophiles to Introduce Versatile Functional Groups At the C-1 Position of Acyclic Moiety

The introduction of versatile functional groups, allyl and ester, at the C-1 position of the acyclic chain in acyclic adenine nucleosides was achieved for the first time directly by alkylation of adenine and N6-protected adenine. Thus, the C-1′-substituted N9-adenine acyclic nucleoside, adenine-9-yl-pent-4-enoic acid ethyl ester (11), was prepared by direct alkylation of adenine with 2-bromopent-4-enoic acid ethyl ester (6), while the corresponding N7-regioisomer, 2-[6, (dimethylaminomethyleneamino)-purin-7-yl]-pent-4-enoic acid ethyl ester (10), was obtained in one step by the coupling of N,N-dimethyl-N′- (9H-purin-6-yl)-formamidine (9) with 2-bromopent-4-enoic acid ethyl ester (6). The functional groups, ester and allyl, were converted to the desired hydroxymethyl and hydroxyethyl groups, and subsequently to phosphonomethyl derivatives and corresponding pyrophosphorylphosphonates.

Synthesis of 9-[1-(1-Hydroxyethyl)-3-(Phosphonomethoxy)Propyl] Adenine and Prodrug as Possible Antiviral Agents

The appropriately protected C-1′-hydroxyethyl-3-hydroxypropyl-N9-adenine nucleoside was prepared from 1-pivaloyloxy-5-tert-butyldiphenylsilyloxy-3-pentanol and adenine through the Mitsunobu reaction. One of the terminal hydroxyls was converted to the phosphonomethoxy derivative and the prodrug.

Synthesis of N6-Substituted 9-[3-(Phosphonomethoxy)Propyl]Adenine Derivatives As Possible Antiviral Agents

A number of N 6 -substituted 9-[3-(phosphonomethoxy)propyl]adenine derivatives having hydroxymethyl at C-1′-position were prepared from the appropriate 6-chloroadenine derivative. The syntheses of the corresponding prodrugs of these compounds are also reported. These compounds showed poor activity against HCV in replicon assay.