We studied the chemical modifications of open-cage fullerene C60 derivatives encapsulating a small molecule such as H2 and H2O. In these reactions, the entrapped molecules can be used as a probe for monitoring the reactions. The solubilizing group (methoxyethyl group) was successfully introduced on the bis(hemiketal) moiety in the open-cage C60 derivative. Further specific reactions were also investigated for 2-methoxyethoxymethyl (MEM)-substituted C60 derivatives.