76142-47-7Relevant academic research and scientific papers
Rh(II)-Catalyzed Reactions of Diazoesters with Organozinc Reagents
Panish, Robert,Selvaraj, Ramajeyam,Fox, Joseph M.
supporting information, p. 3978 - 3981 (2015/09/01)
Rh(II)-catalyzed reactions of diazoesters with organozinc reagents are described. Diorganozinc reagents 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 formation of an azine precedes 1,2-addition by an organozinc reagent. This straightforward route to the hydrazone products provides a useful method for preparing chiral quaternary α-aminoesters or pyrazoles via the Paul-Knorr condensation with 1,3-diketones. Crossover and deuterium labeling experiments provide evidence for the mechanisms proposed.
Structure-Activity Study of Tripeptide Thrombin Inhibitors Using α-Alkyl Amino Acids and Other Conformationally Constrained Amino Acid Substitutions
Shuman, Robert T.,Rothenberger, Robert B.,Campbell, Charles S.,Smith, Gerald F.,Gifford-Moore, Donetta S.,et al.
, p. 4446 - 4453 (2007/10/03)
In our continuing effort to design novel thrombin inhibitors, a series of conformationally constrained amino acids (e.g. α-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 α-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 α-alkylphenylglycine residues resulted in a tendency to exhibit substantional improvements in selectivity over the nonalkylated residues.Combinations of optimal P3 and P2 changes led to compounds TFA-D-Phg(αEt)-Azt-Arg-H (16), TFA-D-Phg(αMe)-Azt-Arg-H (17), Ac-D-Phg(αMe)-Azt-Arg-H (21), TFA-D-Phg(αMe)-Pro-Arg-H (27), 30, and 32, which are clearly more selective for thrombin versus plasmin than the nonconformationally constrained compounds.
