To further derivatize the amino group of compound (6), a free amino compound, or the suitable salt thereof may be treated with an aldehyde or ketone R40C(O)R41 in the presence of a reducing agent such as sodium cyanoborohydride or sodium triacetoxyborohydride to afford compound (7), where R40 and R41 are defined such that R5 in (7) conforms to the specifications for Formula (I).