In addition to ionization conditions, the matrix used in MALDI may play a role in the stability of phosphoester
linkage and its mass analysis.
Because of the greater stability of a phosphodiester linkage, as used in the C3 linker, relative to a single phosphoester
bond, it appears that all of these concerns can be alleviated by replacing the phosphate cap with an alkyl group via common phosphoramidite chemistries.
AR antagonist activity decreased as alkyl chain length of the phosphoester
increased, whereas electron-donating properties of phenyl substituents of the tested compounds did not influence AR activity.