合成路线1

To overcome problems for the previous synthesis, a more efficient, economical and environmentally sound process for the preparation of Sch 37224 was needed. Research toward this goal led to the new synthesis of (I). Salient features of this synthesis are summarized below. Since N-acylation of (II) is reported to be very difficult, a novel, mild, high yielding N-acylation procedure, utilizing propylene oxide as a neutral, irreversible acid scavenger during the N-acylation step, was developed for the conversion of (II) to (VI). The displacement of chlorine from (VI) led to (VII), which proved to be moderately unstable. Hence, mild conditions were developed for an efficient conversion of crude (VII) to (I). The merits of this synthesis are discussed in the literature. This synthesis was used successfully to prepare tens of kilos of (I).