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Földesi, András
Publications (5 of 5) Show all publications
Karimiahmadabadi, M., Erfan, S., Földesi, A. & Chattopadhyaya, J. (2014). Distal Two-Bond versus Three-Bond Electronegative Oxo-Substituent Effect Controls the Kinetics and Thermodynamics of the Conversion of a C-Nitroso Function to the Corresponding Oxime in the Conformationally Locked Pentofuranose (Bicyclo[2.2.1]heptane) System. Journal of Organic Chemistry, 79(16), 7266-7276
Open this publication in new window or tab >>Distal Two-Bond versus Three-Bond Electronegative Oxo-Substituent Effect Controls the Kinetics and Thermodynamics of the Conversion of a C-Nitroso Function to the Corresponding Oxime in the Conformationally Locked Pentofuranose (Bicyclo[2.2.1]heptane) System
2014 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 79, no 16, p. 7266-7276Article in journal (Refereed) Published
Abstract [en]

We report the high-yielding and scalable diastereospecific synthesis of isomeric bicyclo [2.2.1]heptane-7- and -8-oximes and their corresponding C-nitroso derivatives, which are the key intermediates for the synthesis of carbanucleosides. Neither the (C7-R)-nitroso- nor (C8-S)-nitrosobicycloheptane system requires any external base in DMSO-d(6) to afford the corresponding oxime, and no reverse isomerization from the oxime to the C-nitroso compound was observed. The conversion of the (C8-S)-nitroso compound to the E/Z-oximes was similar to 8 times faster (at 40 degrees C) than that of the (C7-R)-nitroso derivative. The mechanism involves first-order reaction kinetics for the conversion of either the (C7-R)- or (C8-S)-nitroso derivative to the corresponding E/Z-oximes. The lower rate of conversion of the (C7-R)-nitroso compound to the corresponding crimes compared with that of the (C8-S)-nitroso derivative is attributed to the fact that the acidic H8 ionizing center is two bonds away from the OPMB group on C1 in the latter whereas H7 is three bonds away from the C1 OMe group in the former, making the effect of the electron-withdrawing group on C1 stronger in the latter.

National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-231998 (URN)10.1021/jo500266k (DOI)000340517600002 ()
Available from: 2014-09-15 Created: 2014-09-12 Last updated: 2017-12-05Bibliographically approved
Upadhayaya, R. S., Dixit, S. S., Földesi, A. & Chattopadhyaya, J. (2013). New antiprotozoal agents: Their synthesis and biological evaluations. Bioorganic & Medicinal Chemistry Letters, 23(9), 2750-2758
Open this publication in new window or tab >>New antiprotozoal agents: Their synthesis and biological evaluations
2013 (English)In: Bioorganic & Medicinal Chemistry Letters, ISSN 0960-894X, E-ISSN 1464-3405, Vol. 23, no 9, p. 2750-2758Article in journal (Refereed) Published
Abstract [en]

Here we report identification of new lead compounds based on quinoline and indenoquinolines with variable side chains as antiprotozoal agents. Quinolines 32, 36 and 37 (Table 1) and indenoquinoline derivatives 14 and 23 (Table 2) inhibit the in vitro growth of the Trypanosoma cruzi, Trypanosoma brucei, Trypanosoma brucei rhodesiense subspecies and Leishmania infantum with IC50 = 0.25 mu M. These five compounds have superior activity to that of the front-line drugs such as benznidazole, nifurtimox and comparable to amphotericin B. Thus these compounds constitute new 'leads' for further structure-activity studies as potential active antiprotozoal agents. 

Keywords
Antiprotozoal agents, Trypanosoma, Leishmania, Parasite inhibitors, Conformationally constrained quinoline
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-200043 (URN)10.1016/j.bmcl.2013.02.054 (DOI)000317333900054 ()
Available from: 2013-05-23 Created: 2013-05-20 Last updated: 2020-06-05Bibliographically approved
Karimi, M., Erfan, S., Földesi, A. & Chattopadhyaya, J. (2012). Steric Effects in the Tuning of the Diastereoselectivity of the Intramolecular Free-Radical Cyclization to an Olefin As Exemplified through the Synthesis of a Carba-Pentofuranose Scaffold. Journal of Organic Chemistry, 77(16), 6855-6872
Open this publication in new window or tab >>Steric Effects in the Tuning of the Diastereoselectivity of the Intramolecular Free-Radical Cyclization to an Olefin As Exemplified through the Synthesis of a Carba-Pentofuranose Scaffold
2012 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 77, no 16, p. 6855-6872Article in journal (Refereed) Published
Abstract [en]

Two free-radical cyclization reactions with the radical at the chiral C4 of the pentose sugar and the intramolecularly C1-tethered olefin (on radical precursors 8 and 17) gave a new diastereospecific C4-C8 bond in dimethylbicyclo[2.2.1]heptane 9, whereas the new C4-C7 bond in 7-methyl-2-oxabicyclo[2.2.1]heptanes 18a/18b gave trans and cis diastereomers, in which the chirality of the C4 center is fully retained as that of the starting material. It has been shown how the chemical nature of the fused carba-pentofuranose scaffolds, dimethylbicyclo[2.2.1]heptane 9 vis-a-vis 7-methyl-2-oxabicyclo[2.2.1]heptanes 18a/18b (C7-Me in the former versus 2-O- in the latter), dictates the stereochemical outcome both at the Grignard reaction step as well as in the free-radical ring-closure reaction. The formation of pure 1,8-trans-bicyclo[2.2.1]heptane 9 from 8 suggests that the boat-like transition state is favored due to the absence of steric clash of the bulky 1(S)-O-p-methoxybenzyl (PMB) and 7(R)-Me substituents (both in the alpha-face) with that of the 8(R)-CH2 center dot radical in the beta-face. The conversion of 17 -> 18a-7(S) and 18b-7(R) in 6:4 ratio shows that the participation of both the chair- and the boat-like transition states is likely.

Keywords
THERMODYNAMIC STABILITIES; CARBOCYCLIC NUCLEOSIDE; MODIFIED OLIGOS; RNASE-H; LNA; OLIGONUCLEOTIDES; ELICITATION; SELECTIVITY; MODULATION; ADENOSINE
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-183898 (URN)10.1021/jo300936g (DOI)000307526700015 ()
Available from: 2012-11-07 Created: 2012-11-05 Last updated: 2017-12-07Bibliographically approved
Karimiahmadabadi, M., Földesi, A. & Chattopadhyaya, J. (2012). Unusual strain-releasing nucleophilic rearrangement of a bicyclo[2.2.1]heptane system to a cyclohexenyl derivative. Journal of Organic Chemistry, 77(21), 9747-9755
Open this publication in new window or tab >>Unusual strain-releasing nucleophilic rearrangement of a bicyclo[2.2.1]heptane system to a cyclohexenyl derivative
2012 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 77, no 21, p. 9747-9755Article in journal (Refereed) Published
Abstract [en]

We report an unusual strain-releasing reaction of 1-mesyloxy-8,7- dimethylbicyclo[2.2.1]heptane (3) by a base-promoted substitution at the chiral C3 followed by spontaneous concerted ring opening involving the most strained C2-C3-C4 bonds (with bond angle 94°) and the C2 bridgehead leading to anti-endo elimination of the C1-mesyloxy group by the conjugate base of adenine or thymine to give two diastereomeric C3′(S) and C3′(R) derivatives of 1-thyminyl and 9-adeninyl cyclohexene: 3 → T-4a + T-4b and 3 → A-5a + A-5b. These products have been unambiguously characterized by detailed 1D and 2D NMR (J-coupling constants and nOe analysis), mass, and UV spectroscopy. Evidence has been presented suggesting that the origin of these diastereomeric C3′(S) and C3′(R) derivatives of 1-thyminyl and 9-adeninyl cyclohexene from 3 is most probably a rearrangement mechanism of a trigonal bipyramidal intermediate formed in the S N2 displacement-ring-opening reaction.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-184927 (URN)10.1021/jo301871d (DOI)000311190200034 ()
Available from: 2012-11-19 Created: 2012-11-15 Last updated: 2017-12-07Bibliographically approved
Upadhayaya, R., Deshpande, S. G., Li, Q., Kardile, R. A., Sayyed, A. Y., Kshirsagar, E. K., . . . Chattopadhyaya, J. (2011). Carba-LNA-5MeC/A/G/T Modified Oligos Show Nucleobase-Specific Modulation of 3′-Exonuclease Activity, Thermodynamic Stability, RNA Selectivity, and RNase H Elicitation: Synthesis and Biochemistry. Journal of Organic Chemistry, 76(11), 4408-4431
Open this publication in new window or tab >>Carba-LNA-5MeC/A/G/T Modified Oligos Show Nucleobase-Specific Modulation of 3′-Exonuclease Activity, Thermodynamic Stability, RNA Selectivity, and RNase H Elicitation: Synthesis and Biochemistry
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2011 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 76, no 11, p. 4408-4431Article in journal (Refereed) Published
Abstract [en]

Using the intramolecular 5-exo-5-hexenyl radical as a key cyclization step, we previously reported an unambiguous synthesis of carba-LNA thymine (cLNA-T), which we subsequently incorporated in antisense oligonudeotides (AON) and investigated their biochemical properties [J. Am. Chem. Soc. 2007, 129 (26), 8362-8379]. These cLNA-T incorporated oligos showed specific RNA affinity of +3.5-5 degrees C/modification for AON:RNA heteroduplexes, which is comparable to what is found for those of LNAs (Locked Nucleic Acids). These modified oligos however showed significantly enhanced nuclease stability (ca. 100 times more) in the blood serum compared to those of the LNA modified counterparts without compromising any RNase H recruitment capability. We herein report the synthesis of 5-methylcytosine-1-yl (C-Me), 9-adeninyl (A), and 9-guaninyl (G) derivatives of cLNA and their oligonucleotides and report their biochemical properties as potential RNA-directed inhibitors. In a series of isosequential carba-LNA modified AONs, we herein show that all the cLNA modified AONs are found to be RNA-selective, but the magnitude of RNA-selectivity of 7'-R-Me-cLNA-G (cLNA-G) (Delta T-m = 2.9 degrees C/modification) and intractable isomeric mixtures of 7'-(S/R)-Me-cLNA-T (cLNA-T, Delta T-m = 2.2 degrees C/modification) was found to be better than diastereomeric mixtures of 7'-(S/R)-Me-cLNA-C-Me with trace of cENA-C-Me (cLNA-C-Me, Delta T-m = 1.8 degrees C/modification) and 7'-R-Me-cLNA-A (cLNA-A, Delta T-m = 0.9 degrees C/modification). cLNA-C-Me modified AONs however exhibited the best nuclease stability, which is 4-, 7-, and 20-fold better, respectively, than cLNA-T, cLNA-A, and cLNA-G modified counterparts, which in turn was more than 100 times stable than that of the native. When the modification sites are appropriately chosen in the AONs, the cLNA-A, -G, and -C-Me modified sites in the AON:RNA hybrids can be easily recognized by RNase H, and the RNA strand of the hybrid is degraded in a specific manner, which is important for the design of oligos for therapeutic purposes. The cLNA-C-Me modified AON/RNA, however, has been found to be degraded 4 times faster than cLNA-A and G modified counterparts. By appropriately choosing the carba-LNA modification sites in AON strands, the digestion of AON:RNA can be either totally repressed or be limited to cleavage at specific sites or at a single site only (similar to that of catalytic RNAzyme or DNAzyme). Considering all physico- and biochemical aspects of cLNA modified oligos, the work suggests that the cLNA modified antisense oligos have the potential of being a promising therapeutic candidate due to their (i) higher nucleobase-specific RNA affinity and RNA selectivity, (ii) greatly improved nuclease stability, and (iii) efficient RNase H recruitment capability, which can induce target RNA cleavage in a very specific manner at multiple or at a single site, in a designed manner.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-155235 (URN)10.1021/jo200073q (DOI)000291128300009 ()
Available from: 2011-06-21 Created: 2011-06-20 Last updated: 2017-12-11Bibliographically approved
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