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Muddala NP, Nammalwar B, Selvaraju S, Bourne CR, Henry M, Bunce RA, Berlin KD, Barrow EW, Barrow WW. Evaluation of New Dihydrophthalazine-Appended 2,4-Diaminopyrimidines against Bacillus anthracis: Improved Syntheses Using a New Pincer Complex. Molecules 2015; 20:7222-44. [PMID: 25905602 PMCID: PMC4445145 DOI: 10.3390/molecules20047222] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 04/14/2015] [Accepted: 04/15/2015] [Indexed: 02/05/2023] Open
Abstract
The synthesis and evaluation of ten new dihydrophthalazine-appended 2,4-diaminopyrimidines as potential drugs to treat Bacillus anthracis is reported. An improved synthesis utilizing a new pincer catalyst, dichlorobis[1-(dicyclohexylphosphanyl)-piperidine]palladium(II), allows the final Heck coupling to be performed at 90 °C using triethylamine as the base. These milder conditions have been used to achieve improved yields for new and previously reported substrates with functional groups that degrade or react at the normal 140 °C reaction temperature. An analytical protocol for separating the S and R enantiomers of two of the most active compounds is also disclosed. Finally, the X-ray structure for the most active enantiomer of the lead compound, (S)-RAB1, is given.
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Affiliation(s)
- Nagendra Prasad Muddala
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - Baskar Nammalwar
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - Subhashini Selvaraju
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - Christina R Bourne
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA.
| | - Mary Henry
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA.
| | - Richard A Bunce
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - K Darrell Berlin
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - Esther W Barrow
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA.
| | - William W Barrow
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA.
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Nammalwar B, Bourne CR, Wakeham N, Bourne PC, Barrow EW, Muddala NP, Bunce RA, Berlin KD, Barrow WW. Modified 2,4-diaminopyrimidine-based dihydrofolate reductase inhibitors as potential drug scaffolds against Bacillus anthracis. Bioorg Med Chem 2014; 23:203-11. [PMID: 25435253 DOI: 10.1016/j.bmc.2014.11.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 10/29/2014] [Accepted: 11/05/2014] [Indexed: 12/14/2022]
Abstract
The current Letter describes the synthesis and biological evaluation of dihydrophthalazine-appended 2,4-diaminopyrimidine (DAP) inhibitors (1) oxidized at the methylene bridge linking the DAP ring to the central aromatic ring and (2) modified at the central ring ether groups. Structures 4a-b incorporating an oxidized methylene bridge showed a decrease in activity, while slightly larger alkyl groups (CH2CH3 vs CH3) on the central ring oxygen atoms (R(2) and R(3)) had a minimal impact on the inhibition. Comparison of the potency data for previously reported RAB1 and BN-53 with the most potent of the new derivatives (19 b and 20a-b) showed similar values for inhibition of cellular growth and direct enzymatic inhibition (MICs 0.5-2 μg/mL). Compounds 29-34 with larger ester and ether groups containing substituted aromatic rings at R(3) exhibited slightly reduced activity (MICs 2-16 μg/mL). One explanation for this attenuated activity could be encroachment of the extended R(3) into the neighboring NADPH co-factor. These results indicate that modest additions to the central ring oxygen atoms are well tolerated, while larger modifications have the potential to act as dual-site inhibitors of dihydrofolate reductase (DHFR).
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Affiliation(s)
- Baskar Nammalwar
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA
| | - Christina R Bourne
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA
| | - Nancy Wakeham
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA
| | - Philip C Bourne
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA
| | - Esther W Barrow
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA
| | - N Prasad Muddala
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA
| | - Richard A Bunce
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - K Darrell Berlin
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA
| | - William W Barrow
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA
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Nammalwar B, Muddala NP, Bourne CR, Henry M, Bourne PC, Bunce RA, Barrow EW, Berlin KD, Barrow WW. Synthesis and biological evaluation of 2,4-diaminopyrimidine-based antifolate drugs against Bacillus anthracis. Molecules 2014; 19:3231-46. [PMID: 24642909 PMCID: PMC4016962 DOI: 10.3390/molecules19033231] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Revised: 03/08/2014] [Accepted: 03/10/2014] [Indexed: 11/16/2022] Open
Abstract
Due to the innate ability of bacteria to develop resistance to available antibiotics, there is a critical need to develop new agents to treat more resilient strains. As a continuation of our research in this area, we have synthesized a series of racemic 2,4-diaminopyrimidine-based drug candidates, and evaluated them against Bacillus anthracis. The structures are comprised of a 2,4-diaminopyrimidine ring, a 3,4-dimethoxybenzyl ring, and an N-acryloyl-substituted 1,2-dihydrophthalazine ring. Various changes were made at the C1 stereocenter of the dihydrophthalazine moiety in the structure, and the biological activity was assessed by measurement of the MIC and K(i) values to identify the most potent drug candidate.
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Affiliation(s)
- Baskar Nammalwar
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - N Prasad Muddala
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - Christina R Bourne
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA.
| | - Mary Henry
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA.
| | - Philip C Bourne
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA.
| | - Richard A Bunce
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - Esther W Barrow
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA.
| | - K Darrell Berlin
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK 74078, USA.
| | - William W Barrow
- Department of Veterinary Pathobiology, Oklahoma State University, 250 McElroy Hall, Stillwater, OK 74078, USA.
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