Retrosynthetic analysis of estrone

Estrone (54, Chart 6) contains a full retron for the o-quinonemethide-Diels-Alder transform which can be directly applied to give 55. This situation, in which the Diels-Alder transform is used early in the retrosynthetic analysis, contrasts with the case of ibogamine (above), or, for example, gibberellic acid (section 6.4), and a Diels-Alder pathway is relatively easy to find and to evaluate. As indicated in Chart 6, retrosynthetic conversion of estrone to 55 produces an intermediate which is subject to further rapid simplification. This general synthetic approach has successfully been applied to estrone and various analogs.  

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Figure 10.20. A convergent retrosynthetic analysis of Velluz s estrone synthesis. Total synthesis of estradiol, schematic. The figures between the individual stages indicate the numbers of reaction steps. ( ) denotes optical resolution at that step.

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