Tandem mass spectra of transition-metal ion adducts of glycosyl dithioacetals; distinction among stereoisomers.
Electrospray ionization mass spectra of some glycosyl dithioacetals recorded in the presence of transition-metal chlorides, XCl2 (where X = Co, Mn and Zn), give abundant adduct ions such as [M+XCl]+ and [2M-H+X]+ and minor ions such as [M-H+X]+ and [2M+XCl]+. The tandem mass spectra of these adducts show characteristic elimination of neutral molecules such as H2O, HCl, EtSH, CH2O, C2H4O2/C2H4O. [M+XCl]+ ions fragment readily and the fragmentation appears to be stereochemically controlled as the relative abundances of the fragments are different for three stereoisomers. The added metal is lost as neutral molecules in the form of XCl(OH) and XCl(SEt). This is a predominant pathway in the ZnCl+ adducts. [2M+XCl]+ ions fragment preferentially by elimination of HCl, indicating strong metal interactions in the resulting dimeric [2M-H+X]+ ion. As there are several electron-rich centers in the molecule, the dimeric complex [2M-H+X]+ can have several structures and the observed fragmentations may reflect the sum of those of all these structures. The dimeric complexes fragment by elimination of neutral molecules leaving the dimeric interactions intact. The extent of fragmentation varies for the stereoisomers, leading to stereochemical differentiation.
Madhusudanan
K P
KP
Sophisticated Analytical Instrument Facility, Central Drug Research Institute, Lucknow-226 001, India. kpmadhusudanan@hotmail.com
Kumar
Brijesh
B
Tiwari
Pallavi
P
Madhusudan
Soni Kamlesh
SK
Misra
A K
AK
D000080:Acetals / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D006031:Glycosylation; D007477:Ions / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism; D013440:Sulfides / Q000737:chemistry*; D028561:Transition Elements / Q000737:chemistry*
D000080:Acetals; D002712:Chlorides; D007477:Ions; D013440:Sulfides; D028561:Transition Elements