A new and powerful method for the synthesis Meyers' bicyclic lactams beginning from furans is reported herein that uses a remarkable one-pot singlet oxygen-initiated cascade reaction sequence to deliver the corresponding bicyclic lactams in high yield. Ever since they were pioneered Meyers' homochiral bicyclic lactams [1, 2] (B, Scheme 1) have been exceedingly popular and versatile scaffolds for the enantioselective construction of new stereogenic centres, including the most challenging typequaternary carbon centres. They have been utilised in myriad different ways to target a wide variety of natural products, [2, 3] nonnatural molecules possessing interesting biological activity, [2, 4] and, also in a diverse array of other synthetic endeavours. [2, 5] The most general method for their synthesis, introduced in the seminal work of Meyers', [1, 2] wherein a γ-ketoacid is condensed with an aminoalcohol under dehydrating conditions in refluxing toluene, is still, by far, the most commonly employed means of accessing the bicyclic scaffold B. Modifications have been made with the aim of introducing milder variants [6] to the Meyers' lactamisation; these Scheme 1. Generalised representation of the transformation achieved with this new methodology.

A highly efficient one-pot transformation of readily accessible furans into 4-hydroxy-2-cyclopentenones in H2O, using singlet oxygen as oxidant, has been developed.

A new set of completely green methods utilising air, light, water and spirulina to transform readily accessible furan substrates into a diverse range of synthetically useful polyoxygenated motifs commonly found in natural products, 10 is presented herein.The ideal green methodology encompasses a host of very different concepts, and, as such, is a far from simple goal to achieve. The practitioner is not just looking for non-polluting, non-toxic reagents to be used in reactions devoid of the 15 traditionally-employed organic solvents, but must also consider ideas such as atom-1 and step-economy, 2 elimination of protecting group usage 3 (and other non-constructive refunctionalisation steps), 4 and overall efficiency for the operation (e.g. the degree to which structural complexity is 20

In this article, we explore how changes in the positioning of pendant hydroxyl functionalities in the photooxygenation substrate dramatically alter the course of furan oxidations that are initiated by singlet oxygen; and, how these different reactivities can be harnessed through cascade reaction sequences to access, rapidly and effectively, a broad range of important natural product motifs.

The key ABC-ring motif of the pectenotoxins has been synthesized, starting from a simple and readily accessible difuran precursor, using a complex singlet oxygen-mediated cascade reaction sequence.