129018-27-5Relevant academic research and scientific papers
Geometric control of a pyridoxal-catalyzed aldol condensation
Koh,Delaude,Breslow
, p. 11234 - 11240 (2007/10/02)
A chiral cyclophane derivative of pyridoxal has been synthesized that has amino groups oriented specifically over one face of the cofactor. The compound catalyzes the formation of threonine and allo-threonine from glycine and acetaldehyde with enantioinductions that are a function of pH, reversing the optical selectivity between low pH and high pH. The stereochemical results are compared with those of structurally related pyridoxal cyclophanes that lack titratable catalytic groups. Explanations are advanced for this stereochemical reversal and for the otherwise surprising preference of most of these compounds to react on the more hindered face of the pyridoxal. Models indicate that the transamination intermediate is distorted by the transannular chain, and stereoelectronic arguments predict that this distortion should lead to reaction on the face that carries the chain, as observed. The stereochemical reversal with the attached (dimethylamino)alkyl group, as a function of pH, may reflect catalysis by the protonated form, but metal coordination by the basic form cannot be excluded.
Synthesis of Tetranuclear Iron-Sulphur Protein Analogues with Tetrathiol Ligands attached to Macrocycles which provide Intramolecular Hydrophobic Domains
Okuno, Hiroaki (Yohmei),Uoto, Kouichi,Tomohiro, Takenori,Youinou, Marie-Therese
, p. 3375 - 3381 (2007/10/02)
A new type of active-site analogues for 4Fe-4S iron-sulphur proteins is introduced, where the active site core is surrounded by an intramolecular hydrophobic domain formed by a 36-membered ring consisting of a methylene backbone.An efficient synthesis of the macrocyclic ligands 1,10,19,28-tetra(4-mercaptobenzoyl)-1,10,19,28-tetra-azacyclohexatriacontane and 1,10,19,28--1,10,19,28-tetra-azacyclohexatriacontane and 1,10,19,28-tetra-(3-mercapto-3-methylbutanoyl)-1,10,19,28-tetra-azacyclohexatriacontane is described.Their reaction with t)4>2- afforded novel clusters in good yields (70 - 90percent) as black powders with m.p. > 300 deg C.They dissolve in dimethylformamide, dimethyl sulphoxide, and propylene carbonate.Complex formation with Fe4S4 clusters was mainly demonstrated by u.v.-visible and n.m.r. studies and the properties of the new clusters are discussed.
