Design and synthesis of an aminobenzo-15-crown-5-labeled estradiol tethered with disulfide linkage

A novel measuring method (electroimmunoassay) of 17β-estradiol (E2) in urine or blood was proposed on the basis of a competition between E2 and a labeled E2 against an immobilizing antibody. To evaluate the principle, 3-{4-[17β-hydroxy-1,3,5(10)-estratrien-3-yloxy]butyldisulfanyl}-N-(6,7,9,10,12,13,15,16-octahydro-5,8,11,14,17-pentaoxabenzocyclopentadecen-2-yl) succinamic acid () was designed and synthesized as a novel aminobenzo-15-crown-5-containing E2 tethered with disulfide linkage. Two thiol-intermediates and were efficiently synthesized from mercaptosuccinic acid and 4,4′-dithiodibutyric acid , respectively. Formations of disulfide linkages from less reactive thiols were examined and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) could be employed for the formation of an unsymmetrical disulfide from and . Then, removal of TMS- and allyl-protecting groups in successfully afforded the crown ether-containing E2 .