The present invention provides a novel a condensed polycyclic compound useful as a phosphodiesterase 4 inhibitor, which is shown by the formula I:or a pharmaceutically acceptable salt thereof and a pharmaceutical composition containing the same. The second region of the substrate may have a higher impurity concentration than an entire region of the substrate other than the second region. The resulting cost savings make it possible for the provider of services to share with the consumer of services a substantial percentage of the payment that the provider receives from a third party payer.