Pyrroles continued with pyrrole aldehydes

The synthesis of calcimycin continued with oxidation of 50, reaction of the aldehyde with 24 to give 51 as a mixture of Cio-diastereomers. Treatment of this mixture with 10-camphorsulfonic acid gave 52. Presumably only the desired Cio diastereomer cyclized to the spiroacetal. The synthesis was completed by reductive cleavage of the N-N bond (pyrrole nitrogen protecting group) and hydrolysis of the trifluoroacetamide and methyl ester. 

Here, the parallels with benzenoid counterparts continue, for these compounds have no special properties - their reactivities are those typical of benzenoid aldehydes, ketones, acids and esters. For example, in contrast to the easy decarboxylation of a-acids observed for pyrrole and furan, thiophene-2-acids do not easily lose carbon dioxide nevertheless, high-temperatme decarboxylations are of preparative value (see also 17.12.1.2). "... 

Numerous 8-substituted BODIPY dyes (te., ones with substituents in the meso position) have been built via condensation of activated carbonyl compounds with readily available pyrroles, especially staring from aldehyde derivatives. Various aldehydes can be utilized to synthesize meso-substituted BODIPYs for adjusting the nature of substituents at the meso position, resulting in a convenient method to achieve more sophisticated functionalities for specialized purposes. In fact, there are many interesting chemical probes based on the synthetic method, which continues to be the most popular route to functionalized BODIPY dyes. ... 

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