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

The synthesis of two novel radiolabelled estrogen derivatives, [I-125](E)-3 -methoxy-17 alpha -iodovinylestra-1,3,5(10),6-tetraen-17 beta -ol (E[I-125] IVDE) and [I-125](Z)-3-methoxy-17 alpha -iodovinylestra-1,3,5(10),6-tetraen -17 beta -ol (Z[I-125]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 synth esised starting from a suitably protected estrone and subsequently converte d into the 17 alpha -ethynyl derivative. The radioiodinated derivatives wer e stereoselectively formed by radioiododestannylation of the corresponding tributylstannyl precursors. The biodistribution of the novel [I-125]iodovin ylestradiol derivatives was evaluated in immature female mice. Biological d ata 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. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.