The present invention aims to provide a compound superior in broad utility and stability, which is useful as a protecting reagent (anchor) of amino acid and/or peptide in liquid phase synthesis and the like of a peptide having a C-terminal etc., which are of a carboxamide (—CONHR)-type, an organic synthesis reaction method (particularly peptide liquid phase synthesis method) using the compound, and a kit for peptide liquid phase synthesis containing the compound, and has found that the object can be achieved by a particular compound having a diphenylmethane skeleton.