Synthesis and host-guest studies of chiral N-linked peptidoresorc[4]arenes.
Four cone resorc[4]arene octamethyl ethers (10, 11, ent-10, and ent-11) tetrafunctionalized at the feet with valyl-leucine [LL- (6); DD- (ent-6)] and leucyl-valine [LL- (9); DD- (ent-9)] methyl esters have been synthesized. These compounds, obtained by conjugation of macrocycle tetracarboxylic acid chlorides with the appropriate terminal amino groups of the above dipeptides, are N-linked peptidoresorc[4]arenes. We found that these macrocycles (M) are capable of recognizing the homologue dipeptides as guests (G), both in solution and in the gas phase, by forming relatively stable host-guest complexes ([M.G]), resistant to chromatographic purification but not to heating. Complexation phenomena between M and G in solution were investigated by NMR methods, including NMR DOSY experiments, for the detection of translational diffusion. Heteroassociation constants of 2030 and 186 M(-1) were obtained by the Foster-Fyfe method for the complexes [10.6] and [10.ent-6], respectively, the latter being comparable to the self-association constant of dipeptide itself. Conversely, the structural features of the proton-bound complexes [M.H.Gn]+ (n = 1, 2), generated in the gas phase by electrospray ionization mass spectrometry (ESI-MS), were investigated by collision-induced dissociation (CID) experiments. In both cases, the four N-linked peptidoresorc[4]arenes were shown to act as synthetic receptors and to recognize the homologue dipeptide by means of hydrogen bonds.
Botta
Bruno
B
Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università La Sapienza, P le Aldo Moro 5, 00185, Roma, Italy. bruno.botta@uniroma1.it
D'Acquarica
Ilaria
I
Monache
Giuliano Delle
GD
Subissati
Deborah
D
Uccello-Barretta
Gloria
G
Mastrini
Massimo
M
Nazzi
Samuele
S
Speranza
Maurizio
M
D047250:Calixarenes / Q000138:chemical synthesis*; D002264:Carboxylic Acids / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D010455:Peptides / Q000737:chemistry*; D012118:Resorcinols / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
D002264:Carboxylic Acids; D002712:Chlorides; D010455:Peptides; D012118:Resorcinols; D047250:Calixarenes; C031389:resorcinol