Conformationally defined neurotransmitter analogs. Selective inhibition of glutamate uptake by one pyrrolidine-2,4-dicarboxylate diastereomer
摘要:
In order to determine the conformational requirements for binding of L-glutamate to the proteins involved in the process of neurotransmission, rigid analogues containing an embedded glutamate moiety have been prepared. These ''conformer mimics'', the pyrrolidine-2,4-dicarboxylates 4, 7, 11, and 14, were synthesized from commercially available trans-4-hydroxy-L-proline and cis-4-hydroxy-D-proline, and then were tested for their ability to inhibit the high-affinity transport of [H-3]-L-glutamate into synaptosomes and to block the binding of radioligands to the NMDA (N-methyl-D-aspartate), KA (kainate), and QA (quisqualate) glutamate neurotransmitter receptor sites. While none of the four analogues binds effectively to the excitatory receptors, the L-trans-isomer 7 is a potent and selective competitive inhibitor of L-glutamate transport. These results delineate a specific structural/conformational preference for binding to the uptake system that is distinct from that required for binding to the NMDA, KA, and QA receptors.
An enantioselective route to pyrrolidines: removal of the chiral template from homochiral pyrroloimidazoles
作者:Raymond C.F. Jones、Kevin J. Howard、John S. Snaith、Alexander J. Blake、Wang-Shei Li、Peter J. Steel
DOI:10.1016/j.tet.2011.08.099
日期:2011.11
Two-step reductive removal of the chiral template from optically active pyrroloimidazoles, available from 1,3-dipolar cycloaddition of homochiral 4,5-dihydroimidazolium ylides, gives optically active substituted pyrrolidines. Selective manipulation of the substituents affords, e.g., naturally occurring and other optically active proline derivatives, and optically active pyrrolizidines and indolizidines
Ene-iminium intermediates resulting from reaction between glyoxal and β-amino alcohols rearrange by an aza-Cope process. Three different tandem reactions are thus carried out; their first component is this cationic rearrangement, the second step being either an iminium hydrolysis, a nucleophile-induced ene-iminium cyclization or a Mannich reaction. The last two sequences lead to homochiral proline
Lactams derived from hetero Diels-Alder adducts were stereospecifically converted into cis-2, 4-pyrrolidinedicarboxylic acid and cis-2, 5-piperidinedicarboxylic acid by ruthenium tetroxide oxidation. Optically active (2S, 4S)-(-)-2, 4-pyrrolidinedicarboxylic acid and (2R, 4R)-(+)-2, 4-pyrrolidinedicarboxylic acid were synthesized from (1S, 4R)-(+)-2-azabicyclo[2.2.1]hept-5-en-3-one and (1R, 4S)-(-)-2-azabicyclo[2.2.1]hept-5-en-3-one, respectively.