Structure-Activity Study of Tripeptide Thrombin Inhibitors Using .alpha.-Alkyl Amino Acids and Other Conformationally Constrained Amino Acid Substitutions
摘要:
In our continuing effort to design novel thrombin inhibitors, a series of conformationally constrained amino acids (e.g. alpha-alkyl, N-alkyl cyclic, etc.) were utilized in a systematic structure-activity study of the P3, P2, and P1 positions of tripeptide arginal thrombin inhibitors. Early examples of this effort include: D-MePhe-Pro-Arg-H (15), Boc-D-Phg-Pro-Arg-H (18), D-1-Tiq-Pro-Arg-H (23, D-1-Tiq D-1,2,3,4-tetrahydroisoquinolin-1-ylcarbonyl), and Boc-D-Phe-Pro-Arg-H (25).(10a,20) The current work clarifies the contribution of each residue of the tripeptide arginals toward the potent and selective inhibition of thrombin relative to that of t-PA and plasmin. The alpha-methylarginal modification in the P1 residue resulted in analogs 30 (D-MePhe at P3) and 32 (D-1-Tiq at P3) which had lower potency toward thrombin while exhibiting improved selectivity. Analogs modified at the P2 site were found to be very sensitive to the conformational changes induced by variations in side chain ring size with the flexible pipecolinic acid 31 being 2 orders of magnitude less potent at thrombin inhibition than the conformationally constrained azetidine analog 20. Examination of the P3 binding region indicated that alpha-alkylphenylglycine residues resulted in a tendency to exhibit substantial improvements in selectivity over the nonalkylated residues. Combinations of optimal P3 and P2 changes led to compounds TFA-D-Phg(alpha Et)-Azt-Arg-H (16), TFA-D-Phg(alpha Me)-Azt-Arg-H (17), Ac-D-Phg(alpha Me)-Azt-Arg-H (21), TFA-D-Phg(alpha Me)-Pro-Arg-H (27), 30, and 32, which are clearly more selective for thrombin versus plasmin than the nonconformationally constrained compounds.
Structure-Activity Study of Tripeptide Thrombin Inhibitors Using .alpha.-Alkyl Amino Acids and Other Conformationally Constrained Amino Acid Substitutions
摘要:
In our continuing effort to design novel thrombin inhibitors, a series of conformationally constrained amino acids (e.g. alpha-alkyl, N-alkyl cyclic, etc.) were utilized in a systematic structure-activity study of the P3, P2, and P1 positions of tripeptide arginal thrombin inhibitors. Early examples of this effort include: D-MePhe-Pro-Arg-H (15), Boc-D-Phg-Pro-Arg-H (18), D-1-Tiq-Pro-Arg-H (23, D-1-Tiq D-1,2,3,4-tetrahydroisoquinolin-1-ylcarbonyl), and Boc-D-Phe-Pro-Arg-H (25).(10a,20) The current work clarifies the contribution of each residue of the tripeptide arginals toward the potent and selective inhibition of thrombin relative to that of t-PA and plasmin. The alpha-methylarginal modification in the P1 residue resulted in analogs 30 (D-MePhe at P3) and 32 (D-1-Tiq at P3) which had lower potency toward thrombin while exhibiting improved selectivity. Analogs modified at the P2 site were found to be very sensitive to the conformational changes induced by variations in side chain ring size with the flexible pipecolinic acid 31 being 2 orders of magnitude less potent at thrombin inhibition than the conformationally constrained azetidine analog 20. Examination of the P3 binding region indicated that alpha-alkylphenylglycine residues resulted in a tendency to exhibit substantial improvements in selectivity over the nonalkylated residues. Combinations of optimal P3 and P2 changes led to compounds TFA-D-Phg(alpha Et)-Azt-Arg-H (16), TFA-D-Phg(alpha Me)-Azt-Arg-H (17), Ac-D-Phg(alpha Me)-Azt-Arg-H (21), TFA-D-Phg(alpha Me)-Pro-Arg-H (27), 30, and 32, which are clearly more selective for thrombin versus plasmin than the nonconformationally constrained compounds.
Rh(II)-Catalyzed Reactions of Diazoesters with Organozinc Reagents
作者:Robert Panish、Ramajeyam Selvaraj、Joseph M. Fox
DOI:10.1021/acs.orglett.5b01836
日期:2015.8.21
Rh(II)-catalyzed reactions of diazoesters with organozinc reagents are described. Diorganozincreagents participate in reactions with diazo compounds by two distinct, catalyst-dependent mechanisms. With bulky diisopropylethyl acetate ligands, the reaction mechanism is proposed to involve initial formation of a Rh-carbene and subsequent carbozincation to give a zinc enolate. With Rh2(OAc)4, it is proposed that initial
Rhodium(III)‐Catalyzed Oxidative Intramolecular 1,1‐Oxyamination of Alkenes with Protected Amino Acids to Produce Oxazoloisoindole‐2,5‐diones
作者:Hiroto Takahashi、Yuki Nagashima、Ken Tanaka
DOI:10.1002/ejoc.202100143
日期:2021.3.26
electron‐deficient bis(ethoxycarbonyl)‐substitutedcyclopentadienyl (CpE) rhodium(III) complex catalyzes the oxidative intramolecular 1,1‐oxyamination of alkenes with N‐benzoyl amino acids to produce oxazoloisoindole‐2,5‐diones. Experimental and theoretical mechanistic studies revealed that this oxidative 1,1‐oxyamination proceeds via not the aza‐Wacker reaction but the formation of a rhoda(III)oxazolidine initiated
Advancing <i>Meta</i>-Selective C–H Amination through Non-Covalent Interactions
作者:Qianqian Lv、Zongxing Hu、Yousong Zhang、Zhihan Zhang、Honghui Lei
DOI:10.1021/jacs.3c09904
日期:2024.1.24
Regioselective C–H amination of simple arenes is highly desirable, but accessing meta-sites of ubiquitous arenes has proven challenging due to the lack of both electronic and spatial preference. This study demonstrates the successful use of various privileged nitrogen-containing functionalities found in pharmaceutical compounds to direct meta-C–H amination of arenes, overcoming the long-standing requirement