Synthesis of Cyclobutane Serine Analogues

In this paper, we describe a thermal [2 + 2] cycloaddition
involving 2-acylaminoacrylates as electron-poor acceptor
alkenes, a reaction that involves a Michael−Dieckmann-type
process. The reaction gives rise to a new substituted cyclobutane skeleton that can be transformed into amino acid
derivatives. For example, a number of transformations were
carried out to give the two pairs of stereoisomers of the
2-hydroxycyclobutane-α-amino acid serine analogue (c4Ser);
compounds 22 and 23. This synthesis covers a gap in
knowledge in the broad field of restricted amino acids.