Retrosynthetic analysis convergent steps

The retrosynthetic analysis is performed in two steps in a first step, SYNGEN dissects the skeleton to find all fully convergent bondsets which utili2e starting material skeletons found in two successive levels of cuts. A bondset is a set of skeletal bonds that is cut during the retrosynthetic analysis or formed in any given synthesis. 

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.

Each intermediate in retrosynthetic analysis is a new target molecule, and combination, in the last step, of the last two intermediates into the TM corresponds to highly convergent synthesis, the advantages of which, compared to consecutive synthesis, have been repeatedly discussed in textbooks on organic synthesis. 

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