On the Synthesis of Stereocalpin A: Partial Retraction/Correction of Previous Results and Rationalization of the Hidden Difficulties

In continuation/checking of a previous synthesis directed toward the literature structure of stereocalpin A it was found that the data for a substantial part of the intermediates reported before were incorrect. Some of the transformations were not successfully reproduced and the failures were shown to be consequences of the presence of the N-Me and the particular location of the ester linkage. The origins of the “extra/minor” signals in the NMR for most of the intermediates, which tend to be mistaken as signs for the presence of impurity/isomers, are also discussed.