Synthesis of constrained phenylalanine derivatives via a [2+2+2] cycloaddition strategy

A simple synthesis of dialkyne building blocks (6, 7, 8 and 9) embodying amino acid moiety is described. The dialkyne 6 participated in a [2+2+2] cycloaddition reaction with various monoalkynes in presence of Wilkinson's catalyst to give 5- and 5,6-disubstituted indan-based a-amino acid derivatives. Cobalt catalyst [e.g., CpCo(CO)<SUB>2</SUB>] has also been employed in the synthesis of various 2-indanyl glycine derivatives via co-trimerization reaction of the diyne building blocks 6 and 7 with several monoalkynes