A practical synthesis of (3-(phenanthren-9-yl)-4,5-dihydroisoxazol-5-yl)methyl (tert-butoxycarbonyl)-L-alaninate

Nitrile oxides are highly reactive, but often unstable, compounds that can be used to substitute for other 1,3-dipoles in [3+2] cycloaddition reactions. Bioorthogonal chemistry reactions that can occur within living systems without interfering with their native biochemical processes, is an area in which stable nitrile oxides can find useful and valuable applications. The rapid and selective synthesis of a phenanthrene-isoxazolyl derivative containing a protected amino acidic residue, through a facile 1,3-dipolar cycloaddition of a stable phenanthrenenitrile oxide to a N-Boc-protected (S)-alanine allyl ester as the dipolarophile is described. The synthetic strategy and the fluorescence properties of the single cycloadduct are presented along with the corresponding analytical and spectroscopic data.