The flow chart for the synthesis of 7α-{7-[8-(biotinamido)-octanamido]-heptyl}-estradiol (compound 7) using E2 (compound 1) as the starting material. The reagents and the reaction conditions used are summarized below: a. Swern oxidation. b. t-BuOK, THF, 0°C, compound 9, −78°C. c. NaBH4, methanol. d. 10% Pd(OH)2/C, H2, 45 psi, ethanol, 60°C 8 h. e. compound 13, Et3N, DMF, rt, 24 h. f. AcOH:MeOH:H2O (4:2:1), rt, 24 h. g. NaI, acetone, reflux, 12 h. h. isobutyl chloroformate, tri-n-butylamine, DMF. i. N-hydroxysuccinimide, dicyclohexyl carbodiimide, DMF.