A spiroisoxazolinoproline-based amino acid scaffold for solid phase and one-bead-one-compound library synthesis

An efficient, multigram synthesis of a spiroisoxazolinoproline-based amino acid, 7, requiring minimal purification, delivering good cis:trans diastereoselectivity (similar to 1:4), and providing good yields is reported. Surface-bound studies of the reduction of an arylnitro group in the presence of an isoxazoline ring with tin(II) dichloride dihydrate were undertaken to confirm the stability of the isoxazoline ring. Full derivitization of this spiroisoxazolinoproline-based amino acid scaffold was performed during the synthesis of a sample library with high yields and high purity that validated the efficiency of the chemistry that was employed in resin-bound library synthesis. A 129 600 member one-bead-one-compound (OBOC) library based on the scaffold 7 was synthesized utilizing a dual amino acid encoding method and bifunctionalization of TentaGel resin.