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Photoreactive phenylalanine derivatives are well known as functional analysis reagents for target biomolecules. The photophores are commonly introduced at 4-position on benzene. Aspartame, which consists of dipeptide L-Asp-L-Phe-OMe, is one of the most utilized artificial sweeteners, and substitution effects on its benzene ring have been reported. Substitution at the 4-position, however, does not maintain its sweetness properties. Trifluoromethyl- diazirine, which is one of the most reliable photophores, was introduced to a different site on phenylalanine and the new photoreactive phenylalanine was converted to aspartame derivatives. The new aspartame derivative had slightly higher sweetness potency than sucrose standard solution.

Simple and stereocontrolled preparation of benzoylated phenylalanine derivatives from optically pure phenylalanine using Friedel-Crafts reaction in trifluoromethanesulfonic acid (TfOH) is reported; these derivatives are useful for photoaffinity labeling. Protected or unprotected phenylalanine derivatives were converted to benzoyl derivatives in TfOH at room temperature in a short time without loss of optical purity. The reaction condition was applied to synthesize novel photoreactive phenylalanine derivative, which has two photophores (benzophenone and diazirine). The detail analysis of photo-irradiation for two different photophores contained phenylalanine derivative was also investigated.

Simple and stereocontrolled preparation of benzoylated phenylalanine derivatives from optically pure phenylalanine using Friedel-Crafts reaction in trifluoromethanesulfonic acid (TfOH) is reported; these derivatives are useful for photoaffinity labeling. Protected or unprotected phenylalanine derivatives were converted to benzoyl derivatives in TfOH at room temperature in a short time without loss of optical purity. The reaction condition was applied to synthesize novel photoreactive phenylalanine derivative, which has two photophores (benzophenone and diazirine). The detail analysis of photo-irradiation for two different photophores contained phenylalanine derivative was also investigated.