ABSTRACT
A method to synthesize benzoxazoles on solid phase using 3-nitrotyrosine as a scaffold has been developed. The synthesis couples N-protected 3-nitrotyrosine to polystyrene via a Wang-type linker. The polymer-supported 3-nitrotyrosine is deprotected and the resultant primary amine converted to a tertiary amine via sequential reductive alkylation using aromatic followed by unhindered aliphatic aldehydes. The phenol is acylated, and the nitro group is reduced using SnCl(2). The resulting amino ester is then dehydratively cyclized to a benzoxazole. The synthesis was developed for a large mix and split (50 x 50 x 50) combinatorial library. The single compounds presented herein represent a diverse array of the types of monomers amenable to the chemistry developed.
Subject(s)
Benzoxazoles/chemical synthesis , Tyrosine/analogs & derivatives , Tyrosine/chemical synthesis , Alkylation , Combinatorial Chemistry Techniques , Cyclization , Drug Evaluation, Preclinical , Magnetic Resonance SpectroscopyABSTRACT
The synthesis of a solid-phase macrolide library is described. The library introduces three sites of diversity to a suitable macrolide scaffold via reductive aminations.
Subject(s)
Erythromycin/analogs & derivatives , Ketolides , Macrolides/chemical synthesis , Azithromycin/chemistry , Clarithromycin/chemistry , Combinatorial Chemistry Techniques , Erythromycin/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure , NinhydrinABSTRACT
The discovery of (+/-)-(2S,3R,4R)-2-(trifluoroacetamido)methyl-3-amino-1-(N'-ethyl-N'-isopropylcarbamyl)pyrrolidine-4-carboxylic acid (A-192558, 20e) as a potent inhibitor of influenza neuraminidase (NA) is described. Efficient syntheses of two core structures, cis-3-(allyloxycarbonyl)amino-1-(9'-fluorenylmethoxycarbonyl)pyrrolidine-4-carboxylic acid (7) and tert-butyl (+/-)-(2S,3R,4R)-2-aminomethyl-3-bis(tert-butyloxycarbonyl)amino-1-(N'-ethyl-N'-isopropylcarbamyl)pyrrolidine-4-carboxylate (18b), were developed. Starting with these core structures and using available structural information of the NA active site as the guide, analogues were synthesized in both the tri- and tetrasubstituted pyrrolidine series by means of high-throughput parallel synthesis in solid or solution phase for expeditious SAR. These studies accelerated the identification of (+/-)-(2S,3R,4R)-2-(trifluoroacetamido)methyl-3-amino-1-(N-ethyl-N-isopropylcarbamyl)pyrrolidine-4-carboxylate (20e, A-192558) as the most potent NA inhibitor in this series (IC50 = 0.2 microM against NA A and 8 microM against NA B). The X-ray crystallographic structure of A-192558 bound to NA revealed the predicted interaction of the carboxylic group with the positively charged pocket (Arg118, Arg292, Arg371) and interaction of the trifluoroacetamino residue with the hydrophobic pocket (Ile222, Trp178) of the enzyme active site. Surprisingly, the ethyl and isopropyl groups of the urea functionality induced a conformational change of Glu276, turning the Glu276/Glu277 hydrophilic pocket, which normally accommodates the triglycerol side chain of substrate sialic acid, into an induced hydrophobic pocket.
Subject(s)
Antiviral Agents/chemical synthesis , Enzyme Inhibitors/chemical synthesis , Neuraminidase/antagonists & inhibitors , Orthomyxoviridae/enzymology , Pyrrolidines/chemical synthesis , Antiviral Agents/chemistry , Crystallography, X-Ray , Drug Design , Enzyme Inhibitors/chemistry , Models, Molecular , Molecular Structure , Pyrrolidines/chemistryABSTRACT
An efficient synthesis of 2-substituted (+/-)-(2R,3R,5R)-tetrahydrofuran-3,5-dicarboxylic acid derivatives has been developed. Starting from 5-norborne-2-ol, the key intermediate (+/-)-methyl 5,6-exo,exo-(isopropylidenedioxy)-2-oxabicyclo[2.2.1]heptane-3-exo-carboxylate (15) was synthesized in an efficient six-step sequence. The key transformation is the base-catalyzed methanolysis-rearrangement of (+/-)-6,7-exo,exo-(isopropylidenedioxy)-4-exo-iodo-2-oxabicyclo[3.2.1]octan-3-one (14). Further manipulation of the 3-substituent of (+/-)-methyl 5,6-exo,exo-(isopropylidenedioxy)-2-oxabicyclo[2.2.1]heptane-3-exo-carboxylate (15) followed by deprotection of the diol moiety and ring opening catalyzed by RuCl(3)/NaIO(4) gave the title compounds in good yield.
Subject(s)
Dicarboxylic Acids/chemical synthesis , Furans/chemical synthesis , Dicarboxylic Acids/chemistry , Furans/chemistry , Magnetic Resonance Spectroscopy , Mass Spectrometry , Molecular StructureABSTRACT
We have used sulfide "Safety Catch" linkers to anchor typical medicinal chemistry functional groups to amine resins. Compounds are loaded as the ester, carbamate, or amine. At the end of the synthesis, the linker is activated by peracid. The sulfone resins are then cleaved by beta-elimination in the gas phase or in solution by secondary amines to produce acids and primary, secondary, or tertiary amines. Comparison of cleavage rates to other sulfone resins including SEM showed significantly faster cleavage for this system with conditions similar to Fmoc deprotection. Application of this strategy to a medicinal chemistry library gives good yields and purities of the resulting compounds.
