Quadrone retrosynthetic analysis

Some illustrative examples from the field of polyquinanes are the synthesis of some derivatives of bicyclo[3.3.0]octane 6 (Scheme 6.7) [12] [15] -which have been used in the total syntheses of coriolin, hirsutic acid and quadrone- and the synthesis of triquinacene 7 and some of its derivatives. The retrosynthetic analysis of perhydrotriquinacene-l,4,7-trione (7a) is shown in Scheme 6.7bis. In the actual synthesis the hydroxy groups must be protected either as trialkylsilyl ethers or more conveniently as benzyl ethers [16] [17]. 

An important feature of the philosophy of retrosynthetic analysis is clearly exposed in the described approaches to the syntheses of quadrone. In general, there are only a few bonds in the target molecule that can be reasonably considered as breakable and even fewer of them as strategic . The selection of the strategic bond will dictate the flavor of the rest of the dismantling down to suitable precursors and hence lead to synthetic plans as varied as those utilized for the the quadrone syntheses. 

The three variations of the retrosynthetic analysis of quadrone discussed in the preceding section were based upon one general concept the sequential bond-after-bond disconnection of the core of the target molecule into a set of smaller fragments. Logistically it is an absolutely reliable approach a consistent... 

Select the strategic bond. This recommendation is especially important in those numerous cases in which the initial analysis does not identify an efficient strategic reaction and, hence, a sequential bond-by-bond dismantling of the structure becomes obligatory. The first bond in this sequence (the strategic bond) defines all subsequent steps in the retrosynthetic analysis. This approach was illustrated in the syntheses of quadrone (Section 3.2.5). 

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