Synthesis of trishomocubane amino acid derivatives

The synthesis of four novel trishomocubane amino acid derivatives is described. The hydantoin precursor and bis-Boc protected hydantoin (>95% yield) were previously reported. A mild hydrolysis of the bis-Boc hydantoin with lithium hydroxide at room temperature quantitatively yielded the corresponding novel cage amino acid. The cage amino acid was characterized as the Fmoc derivative. Although the Fmoc amino acid is partially deprotected after three weeks in a refrigerator, it is stable enough for use in Solid Phase Peptide Synthesis (SPPS). The Fmoc cage amino acid was converted to the acid fluoride with cyanuric fluoride. The acid fluoride is required for activation of the cage amino acid in SPPS. Esterification of the sterically hindered trishomocubane amino acid is also reported, indicating sufficient reactivity of the acid function for potential use in SPPS

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