GRL-0519 (1) is a potent antiviral inhibitor of HIV-1 protease (PR) possessing tristetrahydrofura... more GRL-0519 (1) is a potent antiviral inhibitor of HIV-1 protease (PR) possessing tristetrahydrofuran (tris-THF) at P2. The high resolution X-ray crystal structures of inhibitor 1 in complexes with single substitution mutants PR R8Q , PR D30N , PR I50V , PR I54M , and PR V82A were analyzed in relation to kinetic data. The smaller valine side chain in PR I50V eliminated hydrophobic interactions with inhibitor and the other subunit consistent with 60-fold worse inhibition. Asn30 in PR D30N showed altered interactions with neighboring residues and 18-fold worse inhibition. Mutations V82A and I54M showed compensating structural changes consistent with 6-7-fold lower inhibition. Gln8 in PR R8Q replaced the ionic interactions of wild type Arg8 with hydrogen bond interactions without changing the inhibition significantly. The carbonyl oxygen of Gly48 showed two alternative conformations in all structures likely due to the snug fit of the large tris-THF group in the S2 subsite in agreement with high antiviral efficacy of 1 on resistant virus.
Extreme drug resistant mutant of HIV-1 protease (PR) bearing 20 mutations (PR20) has been studied... more Extreme drug resistant mutant of HIV-1 protease (PR) bearing 20 mutations (PR20) has been studied with the clinical inhibitor amprenavir (1) and two potent antiviral investigational inhibitors GRL-02031 (2) and GRL-0519 (3). Clinical inhibitors are >1000-fold less active on PR20 than on wild type enzyme, which is consistent with dissociation constants (K L) from isothermal titration calorimetry of 40 nM for 3, 178 nM for amprenavir, and 960 nM for 2. High resolution crystal structures of PR20-inhibitor complexes revealed altered interactions compared with the corresponding wild-type PR complexes in agreement with relative inhibition. Amprenavir lacks interactions due to PR20 mutations in the S2/S2′ subsites relative to PR. Inhibitors 2 and 3 lose interactions with Arg8′ in PR20 relative to the wild type enzyme since Arg8′ shifts to interact with mutated L10F side chain. Overall, inhibitor 3 compares favorably with darunavir in affinity for PR20 and shows promise for further development.
Synthesis of novel HIV-1 protease inhibitors incorporating dioxatriquinane-derived P2-ligands is ... more Synthesis of novel HIV-1 protease inhibitors incorporating dioxatriquinane-derived P2-ligands is described. The tricyclic ligand alcohol contains five contiguous chiral centers. The ligand alcohols were prepared in optically active form by an enzymatic asymmetrization of mesodiacetate, cascade radical cyclization, and Lewis acid catalyzed reduction as the key steps. Inhibitors with dioxatriquinane-derived P2-ligands exhibited low nanomolar HIV-1 protease activity.
The total synthesis of the proposed structure of anticancer agent, stereocalpin A is described. T... more The total synthesis of the proposed structure of anticancer agent, stereocalpin A is described. The synthesis features a diastereoselective synthesis of a 5-hydroxy-2,4-dimethyl-3-oxo-octanoic acid unit with asymmetric anti-and syn-aldol reactions as the key steps. Initial cycloamidation led to complete epimerization at the C-11 stereocenter due to unique steric constraints in the 12membered depsipeptide ring. A late stage methylation strategy led to the synthesis of the proposed structure of stereocalpin A. A variety of cyanobacterial metabolites have shown diverse biological properties including antitumor, antibiotic, antiviral, antimycobacterial, analgesic, and antipyretic properties. 1 Stereocalpin A (1), a new cyclic depsipeptide, was isolated from the dry lichen, Ramalina terebrata, of Antarctica in 2008, by Oh et al. 2 Initial testing for cytotoxicity against three human solid tumor cell lines has shown good activity against human colon carcinoma cell lines (HT-29, IC 50 = 6.5 μM), human skin carcinoma cell lines (B16F10, IC 50 = 11.9 μM), and human liver carcinoma cell lines (HepG2, IC 50 = 13.4 μM). In addition, stereocalpin A displayed a protein tyrosine phosphatase 1B (PTP1B) inhibitory activity in a dose-dependent manner with an IC 50 value of 40 μM. Further biological investigations could not be carried out due to the lack of material. The structure of stereocalpin A (1, Figure 1) was elucidated by extensive use of NMR and HPLC analyses of derivatives. Acid degradation (6 N HCl, 120 °C, 24 h) of 1 followed by derivatization with Marfey's reagent 3 and subsequent HPLC analysis revealed that stereocalpin A contains a L-Phe, a L-N-Me-Phe, and a 5-hydroxy-2,4-dimethyl-3-oxooctanoic acid unit, which has not been previously reported as a component of any natural product. The absolute configuration of the octanoate derivative was resolved by a thorough analysis of NOESY data. The unique structure, interesting biological activity, and our interest in cyclic depsipeptides as antitumor agents 4 led us to explore the chemistry and
Synthesis of benzo-fused oxabicyclic systems……………………...S13-S16 7. Evaluation of other carbonyl el... more Synthesis of benzo-fused oxabicyclic systems……………………...S13-S16 7. Evaluation of other carbonyl electrophiles…………..………………S16-S18 S2 I. General Information All reagents were purchased and used without further purification unless otherwise noted. The following reaction solvents were distilled prior to use: Dichloromethane and toluene from calcium hydride, diethyl ether and tetrahydrofuran from Na/Benzophenone. All reactions were carried out under an argon atmosphere in either flame-or oven-dried glassware when moisturesensitive. TLC analysis was run using glass-backed Thin-Layer Silica Gel Chromatography Plates (60 Å, 250 µm thickness, F-254 indicator). Flash chromatography was performed using 230-400 mesh, 60 Å pore diameter silica gel. 1 H and 13 C NMR spectra were recorded at room temperature at 400 MHz and 100 MHz respectively using a QNP probe. Chemical shifts (δ values) are reported in parts per million, and are referenced to the deuterated residual solvent peak. NMR data is reported as: δ value (chemical shift, J-value (Hz), integration, where s = singlet, d = doublet, t = triplet, q = quartet, bs = broad singlet). LRMS and HRMS spectra were recorded at the Purdue University Department of Chemistry Mass Spectrometry Center. Bold and Dashed lines in chemical structures show the relative stereochemistry of the molecule. II. Experiment Details 1. General procedure for synthesizing designated 1,4-diols To a suspension of 2-(3-methoxyphenyl)acetic acid (6), (5.0 g, 30.08 mmol, 1.0 eq) in CH 2 Cl 2 at 0 ºC was added 1,1'-carbonyldiimidazole (CDI) (4.9 g, 30.1 mmol, 1.0 eq). Solution was allowed to stir at that temperature for 1h before the addition of N,O-Dimethylhydroxylamine hydrochloride (3.0 g, 33.1 mmol, 1.1 eq). Upon completion the reaction was quenched with saturated ammonium chloride (10.0 mL). The layers were separated and the aqueous layer was extracted with CH 2 Cl 2 (2 x 15 mL). The organic layers were combined, washed with brine, dried over anhydrous sodium sulfate and concentrated to give the crude product. S3 N-methoxy-2-(3-methoxyphenyl)-N-methylacetamide (3.2 g, 14.3 mmol, 1.0 eq) (or the desired Weinreb amide) was dissolved in tetrahydrofuran (THF) (50 mL). The solution was cooled to-78 ºC; where a 1 M solution of allylMgBr (15.8 mmol, 15.8 mL, 1.1 eq) in THF was added dropwise. The solution was allowed to stir for 1 hour, after which a concentrated solution of NH 4 Cl (20 mL) was added. After warming to room temperature, the reaction was extracted with ethyl acetate (3 x 20 mL). The combined organic layer was washed with brine and dried over anhydrous sodium sulfate. The organic layer was concentrated and purified via column chromatography to yield 2.5 g (86% yield) of the desired allyl ketone. R f = 0.36, 10% ethylacetate/ hexanes. The aforementioned allyl ketone (2.5 g, 12.2 mmol, 1.0 eq) was dissolved in THF (80 mL) and cooled to 0 ºC. BH 3-THF was added dropwise over 10 min. The reaction mixture was stirred for 1h at 0 ºC, then for 1h at room temperature. The reaction mixture was again cooled to 0 ºC and a solution of 30% hydrogen peroxide (2 mL) was added dropwise. A 1.0 M NaOH (20 mL) solution was added after which the reaction was allowed to stir at room temperature for 3 h. The product was extracted using ethyl acetate (3 x 15 mL). The combined organic layer was washed with brine and dried over anhydrous sodium sulfate. The organic layer was filtered, concentrated and purified via column chromatography to yield 1.8 g (67 %) of 1,4-diol 7a. R f = 0.25, 60% ethyl acetate/hexanes. 1 H NMR (400 MHz, CDCl 3) δ 7.22 (t,
Asymmetric multi-component reactions of optically active phenyl dihydrofuran, keto ester or Ntosy... more Asymmetric multi-component reactions of optically active phenyl dihydrofuran, keto ester or Ntosyl imino ester, and allylsilane provided functionalized phenyl tetrahydrofurans with multiple stereogenic centers diastereoselectively. Cleavage of the resulting substituted tetrahydrofurans readily provided acyclic derivatives with three contiguous asymmetric centers via an acyloxycarbenium ion intermediate. Ring closing olefin metathesis, using Grubbs catalyst, afforded functionalized cyclopentene derivatives in optically active form. A one pot tandem tetrahydrofuran ring cleavage followed by ring closing olefin metathesis also provided functionalized cyclopentenes in good yield.
Furan derivatives R 0060 TiCl 4-Promoted Multicomponent Reaction: A New Entry to Functionalized α... more Furan derivatives R 0060 TiCl 4-Promoted Multicomponent Reaction: A New Entry to Functionalized α-Amino Acids.-The multicomponent coupling reaction of N-tosyl imino ester (II), cyclic enol ethers and nucleophiles provides stereocontrolled access to THP-and THF-containing amino acids with multiple stereocenters. The reactions of optically active (X) proceed with excellent diastereoselectivity and good yields.-(GHOSH*, A.
ABSTRACTWe report that GRL-0519, a novel nonpeptidic human immunodeficiency virus type 1 (HIV-1) ... more ABSTRACTWe report that GRL-0519, a novel nonpeptidic human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PI) containingtris-tetrahydrofuranylurethane (tris-THF) and a sulfonamide isostere, is highly potent against laboratory HIV-1 strains and primary clinical isolates (50% effective concentration [EC50], 0.0005 to 0.0007 μM) with minimal cytotoxicity (50% cytotoxic concentration [CC50], 44.6 μM). GRL-0519 blocked the infectivity and replication of HIV-1NL4-3variants selected by up to a 5 μM concentration of ritonavir, lopinavir, or atazanavir (EC50, 0.0028 to 0.0033 μM). GRL-0519 was also potent against multi-PI-resistant clinical HIV-1 variants isolated from patients who no longer responded to existing antiviral regimens after long-term antiretroviral therapy, highly darunavir (DRV)-resistant variants, and HIV-2ROD. The development of resistance against GRL-0519 was substantially delayed compared to other PIs, including amprenavir (APV) and DRV. The effects of nonspecif...
Experimental Section for compounds 3a-5 (S2-S7) 2. References (S-7) 3. 1H and 13C-NMR (S-8- All m... more Experimental Section for compounds 3a-5 (S2-S7) 2. References (S-7) 3. 1H and 13C-NMR (S-8- All melting points were recorded on a Thomas-Hoover melting point apparatus and are uncorrected. 1 H NMR and 13 C NMR spectra were recorded on Varian Oxford 300, Bruker Avance DRX-500 spectrometers. IR spectra were recorded on a Mattason Genesis II FT-IR spectrometer. Optical rotations were recorded on a Perkin Elmer 341 polarimeter. Anhydrous solvents were obtained as follows: THF and diethyl ether by distillation from sodium and benzophenone; pyridine and dichloromethane from CaH 2 . All other solvents were reagent grade. All moisture sensitive reactions were carried out in flame dried flask under nitrogen atmosphere. Column chromatography was performed with Whatman 240-400 mesh silica gel under low pressure of 3-5 psi. TLC was carried out with E. Merck silica gel 60-F-254 plates. The title α-N-tosyl imino ester was made from ethyl glyoxylate and N-toluenesulfonylisocyanate (Aldrich) by Weinreb's procedure 1 . Compounds 6a _ b 2 , 6c 3 , 6d 4 were prepared according to the reported procedures.
We recently reported a number of PIs that were developed by incorporating structure-based designe... more We recently reported a number of PIs that were developed by incorporating structure-based designed novel nonpeptide ligands/scaffolds that target the HIV-1 protease substrate binding site.617 One of the PIs, darunavir (1, DRV, Figure 1), was first approved for HIV/AIDS patients ...
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