An Efficient Synthesis of p-Boronophenylalanine and Its Homologues by the Reaction of Ethyl Isocyanoacetate with a p-Formylbenzeneboronic Acid Derivative
p-Boronophenylalanine (BPA) and its related compounds are worthwhile synthetic targets due to their proven and potential biological activities, particularly with respect to the boron-neutron capture therapy (BNCT) for metastatic melanomas and other tumors. The first synthesis of BPA was achieved by the alkylation of diethyl aminoacetomalonate with p-bromomethylbenzeneboronic acid and subsequent hydrolysis; however, the overall yield was not satisfactory.1) On the other hand, we have developed efficint synthetic routes of nonproteinous amino acids which possess specific functional groups on their side chain using ethyl isocyanoacetate as a synthon.2) These results prompt us to explore a more convenient and practical synthetic route to BPA and its homologues. In this paper, we describe a simple and efficient synthesis of D,L-BPA and p-boronophenylserine (BPS), a new analogue of BPA, via the short routes shown in the schemes.
KeywordsBoronic Acid Othe Hand Efficient Synthesis Sodium Hydride Sodium Cyanide
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