O-Aryl α,ß-d-ribofuranosides: synthesis & highly efficient biocatalytic separation of anomers and evaluation of their Src kinase inhibitory activity.

A series of peracetylated O-aryl α,ß-d-ribofuranosides have been synthesized and an efficient biocatalytic methodology has been developed for the separation of their anomers which was otherwise almost impossible by column chromatographic or other techniques. The incubation of 2,3,5-tri-O-acetyl-1-O-aryl-α,ß-d-ribofuranoside with Lipozyme® TL IM immobilized on silica led to the selective deacetylation of only one acetoxy group, viz the C-5'-O-acetoxy group of the α-anomer over the other acetoxy groups derived from the two secondary hydroxyl groups present in the molecule and also over three acetoxy groups (derived from one primary and two secondary hydroxyls of the ß-anomer). This methodology led to the easy synthesis of both, α- and ß-anomers of O-aryl d-ribofuranosides. All the arylribofuranosides were screened for inhibition of Src kinase. 1-O-(3-Methoxyphenyl)-ß-d-ribofuranoside exhibited the highest activity for inhibition of Src kinase (IC(50)=95.0µM).

Characterization of protein acyltransferase function of recombinant purified GlnA1 from Mycobacterium tuberculosis: a moon lighting property.

The protein acetyltransferase (MTAase) function of glutamine synthetase of Mycobacterium smegmatis was established earlier. In this paper, studies were undertaken to examine MTAase function of recombinant glutamine synthetase (rGlnA1) of Mycobacterium tuberculosis, which showed >80% similarity with M. smegmatis GlnA. The specificity of MTAase to several acyl derivative of coumarins was examined. The results clearly indicated that MTAase exhibited differential specificities to several acyloxycoumarins. Further, MTAase was also found capable of transferring propionyl and butyryl groups from propoxy and butoxy derivatives of 4-methylcoumarin. These observations characterized MTAase in general as a protein acyltransferase. MTAase catalyzed acetylation of GST by 7,8-diacetoxy-4-methylcoumarin (DAMC), a model acetoxy coumarin was confirmed by MALDI-TOF-MS as well as western blot analysis using acetylated lysine polyclonal antibody. In order to validate the active site of rGlnA1 for TAase activity, effect of DAMC and L-methionine-S-sulfoximine (MSO) on GS and TAase activity of rGlnA1 were studied. The results indicated that the active sites of GS and TAase were found different. Acetyl CoA, a universal biological acetyl group donor, was also found to be a substrate for MTAase. These results appropriately characterize glutamine synthetase of Mtb exhibiting transacylase action as a moonlighting protein.

Synthesis, Src kinase inhibitory and anticancer activities of 1-substituted 3-(N-alkyl-N-phenylamino)propane-2-ols.

A series of 3-(N-alkyl-N-phenylamino)propan-2-ol derivatives were synthesized from epichlorohydrine in a multi-step strategy and were evaluated as Src kinase inhibitors. First, epoxy ring opening of epichlorohydrine was carried out in the presence of N-alkylanilines to yield 3-(N-alkyl-N-phenylamino)-1-chloro-propan-2-ol derivatives using Ca(OTf)2 as catalyst based on our previous studies [1]. Second, ring closure was performed under basic conditions to afford N-epoxymethyl N-alkylaniline derivatives. Finally, the epoxide ring opening with four different secondary amines and three nucleobases afforded the final products, i.e., a series of beta-amino alcohols. All compounds were screened for their inhibitory activity against Src kinase and anticancer activity on human breast carcinoma cells, BT-20 cell line. Among all compounds, 3-N-methyl-N-phenylamino-1-(pyrrolidin-1-yl)propan-2-ol (13b) exhibited the highest inhibitory potency (IC50=66.1 microM) against Src kinase. Structure-activity relationship studies suggested that the incorporation of bulky groups at position 1 and N-substitution with groups larger than methyl moiety, reduced the inhibitory potency of the compound significantly. Compounds 3-(N-ethyl-N-phenylamino-)-1-(4-methylpiperazin-1-yl)propan-2-ol (14c) and 3-(N-ethyl-N-phenylamino)-1-(thymine-1-yl)propan-2-ol (17) were found to inhibit the growth of breast carcinoma cells by approximately 45-49% at concentration of 50 microM.

A new oral antiplatelet agent with potent antithrombotic properties: comparison of DZ-697b with clopidogrel a randomised phase I study.

DZ-697b is a new orally active antiplatelet agent that inhibits collagen and ristocetin-mediated platelet activation. It does not require metabolisation to generate its active compound and has a safer profile than clopidogrel in pre-clinical studies. We compared the antithrombotic effects and bleeding time prolongations of three DZ-697b doses with clopidogrel 300 mg. In a four-treatment, three-period, crossover-design, 20 healthy subjects (31 + or - 7 years, 85% males) were randomised to single oral doses of DZ-697b (60, 120 and 360 mg), and clopidogrel (300 mg) (n=15 in each treatment with crossing-over). Antithrombotic effects were assessed by measuring six-hour post-dose changes from baseline in thrombus size in the Badimon chamber and platelet adhesion using Diamed Impact-R platelet function assay. Bleeding times were also measured pre-dose and at six hours post-dose. DZ-697b caused dose-dependent reductions in thrombus size at both high- and low-shear rates (mean reductions at 60, 120 and 360 mg doses of: 13.0%, 18.7%, 26.4% and 11.4%, 12.7%, 22.1% respectively, p<0.05 for all). Effect of clopidogrel (reductions of 18.7% and 11.0% respectively, p<0.05 for both) was closest to DZ-697b 120 mg. Reductions in platelet adhesion were also dose-dependent. Bleeding time ratio from baseline were shorter with DZ-697b versus clopidogrel (1.3, 1.4 and 1.5 versus 1.9, p<0.05 for all). The oral agent DZ-697b shows potent, dose-dependent, antithrombotic effects that are comparable to 300 mg clopidogrel at the 120 mg dose. Despite having equal or greater antiplatelet potency than 300 mg clopidogrel, bleeding time prolongations are significantly shorter with DZ-697b.

Greener biocatalytic approach to the synthesis of nucleosides and their precursors.

Novel, efficient and selective biocatalytic acylation / deacylation strategies have been used for the greener synthesis of precursors of different bicyclonucleosides. Biocatalytic methodology has also been developed for the separation of pyrano- and furanonucleosides, which is otherwise almost impossible to achieve by usual chemical approach.