Cyclobutane Biomolecules: Synthetic Approaches to Amino Acids, Peptides and Nucleosides

Among the natural or designed products containing the cyclobutane moiety, amino acids and nucleosides are relevant. Some of these compounds are receiving much attention due to their biological properties as antibiotics, and antiviral or antitumoral agents. Synthetic approaches to these compounds are considered in this review, based on [2+2]- photocycloadditions or on the use of suitable precursors bearing the pre-formed cyclobutane ring. Absolute chirality is determined by the use of chiral precursors, i.e. terpenes, through chemoenzimatic resolutions, or by using chiral reagents and catalysts. Functionalization of the carbocyclic ring, a feature of crucial relevance, is the other synthetic challenge to be considered. More of ninety recent works are referred.