PURPOSE: To obtain a new compound useful as a synthetic intermediate for thiol protease inhibitors excellent in oral absorbability, tissual migrating properties and cell membrane permeability.
CONSTITUTION: The compound of formula I [R1 is protecting group of amino; R2 is H, 1-5C alkyl or protecting group of amino; R3 is H or (substituted) 1-15C alkyl; R4 is H or 1-5C alkyl; R1 and R2 may be linked to form phthalyl; R3 and R4 may be linked to form 3-10C cycloalkyl; R5 is H, 1-15C alkyl, 3-10C cycloalkyl, etc.], e.g. 2-[(2S)-2-tert-butoxycarbonylamino-1-hydroxyhexyl) cyclopropenone. This compound of formula I is obtained by reacting a cyclopropenone ketal derivative of formula II with an aldehyde derivative of formula III, providing a cyclopropene ketal derivative of formula IV and subsequently deprotecting the resultant compound with an acid or a cation-exchange resin. The compound is capable of manifesting strong inhibiting activity against a thiol protease such as calpain, papain, cathepsin B, cathepsin H or cathepsin L.
ANDO RYOICHI
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