Synthesis and biological evaluation of two new radiolabelled estrogens: [¹²⁵I](E)-3-methoxy-17α-iodovinylestra-1,3,5(10),6-tetraen-17β-ol and [¹²⁵I](Z)-3-methoxy-17α-iodovinylestra-1,3,5(10),6-tetraen-17β-ol

The synthesis of two novel radiolabelled estrogen derivatives, [¹²⁵I](E)-3-methoxy-17α-iodovinylestra-1,3,5(10),6-tetraen-17β-ol (E[¹²⁵I]IVDE) and [¹²⁵I](Z)-3-methoxy-17α-iodovinylestra-1,3,5(10),6-tetraen-17β-ol (Z[¹²⁵I]IVDE), was carried out aiming to study the influence of the introduction of a C6-C7 double bond on the biological properties of the estradiol molecule. 3-Methoxyestra-1,3,5(10),6-tetraen-17-one was synthesised starting from a suitably protected estrone and subsequently converted into the 17α-ethynyl derivative. The radioiodinated derivatives were stereoselectively formed by radioiododestannylation of the corresponding tributylstannyl precursors. The biodistribution of the novel [¹²⁵I]iodovinylestradiol derivatives was evaluated in immature female mice. Biological data indicated that the Z-isomer, owing to its higher in vivo uptake by the target tissue, has the preferable configuration for further development of similar compounds for estrogen receptor detection. Copyright (C) 2001 Elsevier Science Ltd.