Design and Synthesis of Novel Symmetric Fluorene-2,7-Diamine Derivatives as Potent Hepatitis C Virus Inhibitors

Hepatitis C virus (HCV) is an international challenge. Since the discovery of NS5A direct-acting antivirals, researchers turned their attention to pursue novel NS5A inhibitors with optimized design and structure. Herein we explore highly potent hepatitis C virus (HCV) NS5A inhibitors; the novel analogs share a common symmetrical prolinamide 2,7-diaminofluorene scaffold. Modification of the 2,7-diaminofluorene backbone included the use of (S)-prolinamide or its isostere (S,R)-piperidine-3-caboxamide, both bearing different amino acid residues with terminal carbamate groups. Compound 26 exhibited potent inhibitory activity against HCV genotype (GT) 1b (effective concentration (EC50) = 36 pM and a selectivity index of >2.78 × 106). Compound 26 showed high selectivity on GT 1b versus GT 4a. Interestingly, it showed a significant antiviral effect against GT 3a (EC50 = 1.2 nM). The structure-activity relationship (SAR) analysis revealed that picomolar inhibitory activity was attained with the use of S-prolinamide capped with R- isoleucine or R-phenylglycine residues bearing a terminal alkyl carbamate group.

Syntheses of Enantiopure 1,2-Ethylenediamines with Tethered Secondary Amines of the Formula H2NCH2CH[(CH2) n NHMe]NH2 (n = 1–4) from α-Amino Acids: New Agents for Asymmetric Catalysis

Tris(hydrochloride) adducts of the title compounds­ are prepared from the inexpensive α-amino acids H2N(C=O)CH2CH(NH2)CO2H, HO(C=O)(CH2) n′CH(NH2)CO2H (n′ = 1, 2), and H2N(CH2)4CH(NH2)CO2H, respectively (steps/overall yield = 5/32%, 7/30%, 7/33%, 5/38%). The NH2 group that is remote from the secondary amine is installed via BH3 reduction of an amide [–(C=O)NR2] derived­ from an α-amino carboxylic acid. The MeNHCH2 units are introduced by BH3 reductions of alkyl carbamate [RO(C=O)NHCH2–; R = Et, t-Bu] or amide [MeHN(C=O)–] moieties.

Environmental-Friendly Synthesis of Alkyl Carbamates from Urea and Alcohols with Silica Gel Supported Catalysts

TiO2/SiO2, Cr2O3-NiO/SiO2, and TiO2-Cr2O3/SiO2 were prepared by the impregnation method for alkyl carbamate synthesis using urea as the carbonyl source. Up to 97.5% methyl carbamate yield, 97% ethyl carbamate yield, and 96% butyl carbamate yield could be achieved, respectively. The catalysts were characterized by ICP-AES, BET, XRD, XPS, NH3-TPD, and EPMA. Catalytic activity investigation revealed that TiO2/SiO2, Cr2O3-NiO/SiO2, and TiO2-Cr2O3/SiO2 were effective catalysts for methyl carbamate (MC), ethyl carbamate (EC), and butyl carbamate (BC), respectively. The recycling tests suggested that these silica gel supported catalyst system is active, stable, and reusable. A total of 96–97% alkyl carbamate (methyl, ethyl, and butyl) could be obtained in a 2 L autoclave, and these data suggested that our catalyst system is relatively easy to scale up.