Yunhui Wu

Chiral non-racemic C60 derivatives: A proposed sector rule for fullerene absolute configuration

Abstract A number of higher fullerenes as well as carbon nanotubes have been predicted to be chiral. Our lab has recently reported the resolution and CD spectra of several enantiomeric C 60 derivatives. It appears that chromatographic resolutions using Whelk-O columns are rather general. Using optically active enones and dienes, non-racemic C 60 adducts can also be formed. Recently we have discovered that fullerene CD spectra appear to arise from a UV band diagnostic for reaction at the CC bond between two six membered rings, the most common site for mono-addition. A Cotton effect is observed in the CD associated with this chromophore and allows proposal of a sector rule for fullerene chirality. Preparation of chiral (non-racemic) fullerene adducts of known absolute configuration allows assignment of the sign to each of the sectors. These CD bands are due to asymmetric perturbation of an intrinsically symmetric chromophore and provide a new tool for a priori determination of absolute configuration.

Crown ether fulleroids and their detection in solution by electrospray MS

The attachment of a crown ether to the surface of fullerene molecules facilitates their detection by electrospray mass spectrometry.

Electrospray ionization mass spectrometry of vitamin D derivatives

Abstract Selective “electrospray active” tagging reagents allow the introduction of a chargeable group into neutral vitamin D molecules so they may be detected by electrospray mass spectrometry. An amino group or a crown ether are introduced via the Diels-Alder reaction of the corresponding substituted maleimides with vitamin D.

Selective alkali metal binding of valinomycin by electrospray ionization mass spectometry

Abstract Selective binding of alkali metal ions by the ionophore antibiotic valinomycin in alcoholic media was detected by electrospray ionization mass spectrometry (ESI-MS). The relative cation affinity for valinomycin is in the order Rb+ > Cs+ > K+ ≫ Na+ in both methanol and ethanol. With a 1:1:1 mixture of valinomycin and synthetic mimics 18-crown-6 and [2,2,2]-cryptate (methanol, excess KOAc) valinomycin showed much higher affinity than the other ionophores. This study has shown that the potential of ESI-MS as a very useful tool for research involving metal binding is great. Problems with sodium ion interference and quantitation are discussed.

Analysis of vitamin D and its metabolites : derivatization and detection by electrospray ionization mass spectrometry

N-(Benzo-15-crown-5)-1,2,4-tyriazol-3,5-dione is used to prepare an ‘electrospray active’ derivative of vitamin D; this general method could be applied to electrospray ionisation mass spectrometry of biomedically important products, which are not normally observable.

Characterization of Alkaloids By Electrospray Mass Spectrometry

Abstract Electrospray ionization mass spectrometry is a useful new technique for structure determination of alkaloids in solution. Incredibly clean spectra of quinine, strychnine, solasodine, yohimbine, pentazocine and metazocine show only the protonated molecular ion. Increasing the repeller voltage leads to fragmentation showing structural information similar to EI. Non-basic alkaloids such as colchicine show much weaker M+H+ and M+Na+ ions.

Functionalization of C60 by Cycloaddition Reactions

Functionalization of C 60 has been achieved by [2+2] photocycloaddition reactions of enones and [2+4] cycloaddition reactions of dienes, the course of these reactions can be followed using electrospray mass spectrometry using a special tagging reagent. Using tagged C60 it was shown that cis and trans cycloadducts are formed from ketones such as 3-methylcyclohexenone. We have also employed the new technique of 3 He NMR spectrometry. 3 He is an NMR-active nucleus. Fullerenes containing an endohedral 3 He atom can be examined by NMR to obtain structural information and potentially determine isomer distributions. Examples, of helium spectra of fullerene hydrides are presented.