| Popis: |
This chapter is the review of developments in the physical properties, synthesis, and applications of fused bicyclic, tricyclic, and polycyclic azetes, azetines, and azetidines in the last decade. A noticeable feature is the increased number of fused rings in the compounds reported and hence the increasingly complex stereochemistry which is established by sophisticated spectroscopic techniques and X-ray crystallography. There are major developments in the synthesis and application of tricyclic carbapenems known as trinems (formerly called tribactams), especially due to their valuable therapeutic activity. Significant advances are described in the chemistry of polycyclic β-lactams and other compounds either having nitrogen or without nitrogen at the bridgehead. New approaches to these fused systems by radical, Kinugasa, and Pauson–Khand reactions and carbene-catalyzed metathesis cyclizations are reported. Further examples are given of reactions and syntheses mentioned in CHEC-II(1996). Compounds having five fused four-membered rings containing a β-lactam at the terminus are described. Therapeutic use and potential activity of several compounds are mentioned. This chapter describes how fused β-lactams with known absolute stereochemistry have been used to obtain the corresponding β-amino acids and how some β-lactams have been employed as synthons in routes to other heterocycles. |
