174698-95-4Relevant articles and documents
Synthesis and folding propensity of aliphatic oligoureas containing repeats of proline-type units
Fremaux, Juliette,Kauffmann, Brice,Guichard, Gilles
, p. 5494 - 5502 (2014)
The synthesis and conformational analysis of aliphatic oligoureas containing multiple adjacent N-alkylated units derived from proline (i.e., Prou) are reported. The insertion of trisubstituted ureas in the main chain of N,N′-linked oligourea fo
Basicities and Nucleophilicities of Pyrrolidines and Imidazolidinones Used as Organocatalysts
An, Feng,Maji, Biplab,Min, Elizabeth,Ofial, Armin R.,Mayr, Herbert
supporting information, p. 1526 - 1547 (2020/02/04)
The Br?nsted basicities pKaH (i.e., pKa of the conjugate acids) of 32 pyrrolidines and imidazolidinones, commonly used in organocatalytic reactions, have been determined photometrically in acetonitrile solution using CH acids as indicators. Most investigated pyrrolidines have basicities in the range 16 aH aH aH 12.6) and the 2-imidazoliummethyl-substituted pyrrolidine A21 (pKaH 11.1) are outside the typical range for pyrrolidines with basicities comparable to those of imidazolidinones. Kinetics of the reactions of these 32 organocatalysts with benzhydrylium ions (Ar2CH+) and structurally related quinone methides, common reference electrophiles for quantifying nucleophilic reactivities, have been measured photometrically. Most reactions followed second-order kinetics, first order in amine and first order in electrophile. More complex kinetics were observed for the reactions of imidazolidinones and several pyrrolidines carrying bulky 2-substituents, due to reversibility of the initial attack of the amines at the electrophiles followed by rate-determining deprotonation of the intermediate ammonium ions. In the presence of 2,4,6-collidine or 2,6-di-tert-butyl-4-methyl-pyridine, the deprotonation of the initial adducts became faster, which allowed the rate of the attack of the amines at the electrophiles to be determined. The resulting second-order rate constants k2 followed the correlation log?k2(20 °C) = sN(N + E), where electrophiles are characterized by one parameter (E) and nucleophiles are characterized by the two solvent-dependent parameters N and sN. In this way, the organocatalysts A1-A32 were integrated in our comprehensive nucleophilicity scale, which compares n-, -, and σ-nucleophiles. The nucleophilic reactivities of the title compounds correlate only poorly with their Br?nsted basicities.
Role of Configuration at C6 in Catalytic Activity of l-Proline-Derived Bifunctional Organocatalysts
Jin, Hui,Cho, Soo Min,Lee, Juyeol,Ryu, Do Hyun
supporting information, p. 2434 - 2437 (2017/05/12)
l-Proline-derived chiral bifunctional (thio)urea organocatalysts epi-PTU and epi-PU were newly synthesized, and their catalytic performances were compared with their C6 epimeric catalysts PTU and PU in various Michael reactions of nitrostyrene in terms of reactivities and stereoselectivities. The experimental results indicate that a proper relative stereochemistry at C2 and C6 in l-proline-derived bifunctional organocatalysts is important for successful catalysis and that catalysts (PTU and PU) with the 2S,6R configuration are much more efficient.
Inducing achiral aliphatic oligoureas to fold into helical conformations
Wechsel, Romina,Maury, Julien,Fremaux, Juliette,France, Scott P.,Guichard, Gilles,Clayden, Jonathan
supporting information, p. 15006 - 15009 (2014/12/11)
The ability of urea-linked oligomers of achiral diamines (achiral analogues of the well-established chiral oligourea foldamers) to adopt helical conformations was explored spectroscopically. Up to four achiral units were ligated either to a well-formed helical trimer or to a single chiral diamine, and the extent to which they adopted a screw-sense preference was determined by NMR and CD. In the best performing cases, a trimeric chiral oligourea and even a single cis-cyclohexanediamine monomer induced folding into a helical conformation.
Syntheis of new chiral 5,6,7,8-tetrahydrotetrazolo[1,5-a]pyrazines from α-amino acid derivatives following "click" chemistry
Mohapatra, Debendra K.,Maity, Pradip K.,Ghorpade, Ravindra V.,Gurjar, Mukund K.
scheme or table, p. 865 - 872 (2010/09/16)
An efficient and practical synthesis of new chiral fused tetrazoles have been synthesized following [3+2] cycloaddition reaction starting from α-amino acid derivatives.
Synthesis of new chiral 4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyrazines from α-amino acid derivatives under mild conditions
Mohapatra, Debendra K.,Maity, Pradip K.,Gonnade, Rajesh G.,Chorghade, Mukund S.,Gurjar, Mukund K.
, p. 1893 - 1896 (2008/03/13)
A practical and efficient regioselective synthesis of several new chiral 4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyrazines is described from α-amino acid derivatives following intramolecular 'click' reaction as the key step. The method obviates product pu
Evolution of pyrrolidine-type asymmetric organocatalysts by "click" chemistry
Luo, Sanzhong,Xu, Hui,Mi, Xueling,Li, Jiuyuan,Zheng, Xiaoxi,Cheng, Jin-Pei
, p. 9244 - 9247 (2007/10/03)
(Chemical Equation Presented) Click chemistry has been employed to construct a library of the pyrrolidine-type asymmetric organocatalysts. The clicked organocatalysts were evaluated in asymmetric Michael addition of ketones to nitroolefins, showing good c
Thrombin active site inhibitors: Chemical synthesis, in vitro and in vivo pharmacological profile of a novel and selective agent BMS-189090 and analogues
Das, Jagabandhu,Kimball,Reid, Joyce A.,Wang, Tammy C.,Lau, Wan F.,Roberts, Daniel G.M.,Seiler, Steven M.,Schumacher, William A.,Ogletree, Martin L.
, p. 41 - 44 (2007/10/03)
A series of structurally novel small molecule inhibitors of human α-thrombin was prepared to elucidate their structure- activity relationships (SAR), selectivity and activity in vivo. BMS-189090 (5) is identified as a potent, selective, and reversible inh