A two-directional synthesis of the C58-C71 fragment of palytoxin

A two directional approach, in which asymmetric dihydroxylation and reduction reactions were used to control absolute configuration, was exploited in the preparation of a C-2-symmetrical dipyranone. The homotopic dihydropyran (DHP) rings of this precursor were differentiated statistically using by a Prevost reaction and further functionalisation. A second Prevost reaction was used to functionalise the other DHP; global deprotection and peracetylation gave a protected version of the C-58-C-71 fragment of palytoxin. Methods which might be of value in future synthetic work were developed for the stereoselective functionalisation of THP rings similar to those found in this fragment.