Optically Active Calixarenes Conduced by Methylene Substitution

Abstract

All reactions were run using either oven-dried or flame-dried glassware under an inert atmosphere of argon. Chemicals used were reagent grade and used as supplied except where noted. The following solvents were distilled from the listed drying agents: Tetrahydrofuran (Na, benzophenone), diethyl ether (Na, benzophenone), toluene (Na), dichloromethane (CaH 2 ). Anhydrous1,2 dichloroethane was purchased from Aldrich and used under atmosphere of argon. Molecular sieves (4Å) 1/16" pellets were dried in oven over 2-3 days at 125-140ºC prior to use. Silver nitrate (99.9995 % Ag) was purchased from Strem chemicals. Chromatographic purifications were performed on Merck silica gel grade (230-400 mesh) by step gradient elution method starting from 5 % ethyl acetate / hexanes unless otherwise mentioned and TLC's were performed on plastic baked TLC plates from Silicycles. The general solvent systems used were either a combination of ethyl acetate / hexanes or dichloromethane / hexanes unless otherwise specified. Compounds were visualized by dipping in solution of KMnO 4 followed by heating with a heat-gun. 1 H NMR data obtained either on a Varian 300 MHz or 500 MHz instrument are reported in parts per million (δ) relative to tetramethyl silane (0.00 ppm) or chloroform (7.24 ppm) for spectra run in CDCl 3 and multiplicities are indicated by s (singlet), d (doublet), t (triplet), q (quartet), dd (doublet of doublets), dt (doublet of triplets) and br (broad). 13 C NMR data were obtained on the Varian 300 MHz or 500 MHz instruments respectively and are reported in δ relative to CDCl 3 (77 ppm). Infrared spectra were recorded on Perkin Elmer FT IR instrument and the peaks are reported in cm -1 with indicated relative intensities: s (strong), m (medium), w (weak), brs (broad and strong). 1-D NOE experiments and NOESY experiments were performed on a Varian 600 MHz NMR instrument. Mass spectral data and elemental analysis were obtained from Michigan State University Biochemistry Mass spectrometry facility and in-house facility. The mass spectra were obtained using direct probe EI using chloroform as solvent on JEOL AX-505 double focusing mass spectometer, FAB conditions using 2-Nitrobenzyl alcohol as solvent on JEOL HX-110 double focusing mass spectrometer in the positive ionization mode. Data are reported in the form of m/z (intensity relative to base peak = 100). 2,6-diformyl-4-methyl anisole was prepared by Swern oxidation of 2,6-bis-hydroxymethyl-4-methyl anisole following literature procedure 1 .The synthesis of carbene complex 13a was reported in an earlier communication. 2 Organo-lithium reagents were purchased from Aldrich and titrated to a known concentration following the procedure of Gilman. 3 The indicated reaction temperatures are of the oil bath temperature monitored by a digital temperature controller. The reactions were often monitored for completion by quenching an aliquot of the reaction mixture in ether/water and ethereal layer was subjected to GC/MS analyses on Saturn 2000R mass spectrometer and 3800GC using chro...

Regulating the Conformation of Methylazacalix[6]pyridine by Oligonucleotide BCL-2 2345 and Its Recognition of Hydroxymethylpiperazinofullerene

“…33−35 Furthermore, achiral MACP6 has been shown as a strongest monomacrocyclic host in complexation with C 60 and C 70 . 14,16,36 One may expect MACP6 with various chiralities to show different recognition ability. Herein, an approach to obtain various conformations of MACP6 templated by oligonucleotide bcl-2 2345 and their recognition for hydroxymethylpiperazinofullerene (abbreviated as C 60 -T) (Figure 1), a fullerene derivative, 37 have been presented.…”

“…Calixaromatics have attracted much attention on molecular recognition owing to their interesting conformations, cavity structures, versatile recognition properties, and functions. − Research on calixaromatics’ conformation has been promoted with the development of calixaromatic chemistry, which mainly focus on synthesis of inherently chiral forms of calxiaromatics − in terms of creation of chiral spaces for enzyme mimics and chiral recognition. − As for calixarenes, introducing an achiral substituent into the upper and/or lower rims may create molecular dissymmetry or asymmetry to form inherently chiral calixarenes. ,,,− However, such processes are generally delicate and difficult for the more flexible calixaromatics with a larger cycle. Therefore, control of the calixaromatics' conformation is still a challenging topic in the field of calixaromatics, although the conformational isomers determined by crystallography, , NMR, , and theoretical computation , have been widely studied.…”

“…This binding results from the preferred interaction of MACP6 to the loop of the G-quadruplex and depends on the nature of the nucleotide in the loop. This result has offered us a good chance to regulate the chirality of MACP6 by changing the DNA structure because the G-quadruplex DNA structure is very sensitive to the environment. − Furthermore, achiral MACP6 has been shown as a strongest monomacrocyclic host in complexation with C 60 and C 70 . ,, One may expect MACP6 with various chiralities to show different recognition ability. Herein, an approach to obtain various conformations of MACP6 templated by oligonucleotide bcl-2 2345 and their recognition for hydroxymethylpiperazinofullerene (abbreviated as C 60 -T) (Figure ), a fullerene derivative, have been presented.…”