Studies on strigolactone BC-ring formation: Chemical conversion of an 18-hydroxycarlactonoate derivative into racemic 4-deoxyorobanchol/5-deoxystrigol via the acid-mediated cascade cyclization.

[Display omitted] • The BC-rings of canonical SL was constructed by the acid-mediated cascade cyclization. • An 18-hydroxycarlactonoate derivative was successfully converted to rac -4DO/5DS. • The cyclization demonstrated "in flask" may be analogous to that in planta. • The 4π-electrocyclic reaction-based mechanism is proposed. Strigolactones are a group of apocarotenoids known as rhizosphere semiochemicals and phytohormones. Canonical strigolactone consists of a tricyclic lactone (ABC-rings) and a butenolide moiety (D-ring). Although strigolactone biosynthesis has been extensively studied, the process of BC-ring formation has not been elucidated to date. In this study, the chemical conversion of an 18-hydroxycarlactonoate derivative into racemic 4-deoxyorobanchol/5-deoxystrigol was achieved by the acid-mediated cascade cyclization. The acid-mediated BC-ring formation may offer inspiring suggestion for the currently unclear BC-ring formation in strigolactone biosynthesis. [ABSTRACT FROM AUTHOR]