This first retrosynthetic step involves the intramolecular version of an esterifcation reaction. The generalized forward reaction is simply ROH + R'COOH (with acid or basic catalysis), where both functional groups are present in the same molecule.
Analyzing the next target, A, one recognizes the alpha beta unsaturated carbonyl pattern, which is suggestive of an aldol condensation.

In the forward sense, this reaction would be best carried out by using the enolate derived from C, with subsequent hydrolysis and decarboxylation, as outlined below.

Fragment B contains a 1,3 oxygenation pattern -- more sepcifically a beta hydroxy aldehyde, a recognizable aldol product.
In the evaluation of the forward step, we again see that while this is a mixed aldol reaction, there is only one position with an enolizable proton, and the reaction is deemed feasible.
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