Synthetic Pathways to HPB Ester

In a recent literature survey we found 91 papers and patents reporting the synthesis of enantiomerically pure or racemic HPB ester, more than 20 of these appearing in the last two years. This shows the enormous interest in this valuable syn-thon and Fig. 2 depicts the three best pathways to 1. 

From the descriptions in the literature it is hard to judge which of the many methods described are feasible on a technical scale, and procedures for large-scale preparations are described only very rarely. 

This chapter will focus on the comparison of four enantioselective reduction routes A-D developed over the last two decades by Ciba-Geigy and/or Solvias in 

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