Total Syntheses of Furaquinocin A, B, and E

A modular approach to the total synthesis of furaquinocins culminated in the total syntheses of
furaquinocin A, B, and E. A Pd-catalyzed dynamic kinetic asymmetric transformation (DYKAT) on carbonates
derived from Baylis−Hillman adducts, followed by a reductive Heck cyclization allows the enantio- and
diastereoselective construction of dihydrobenzofuran 32. Introduction of a double unsatured side chain via
Horner−Wadsworth−Emmons reaction and assembly of the naphthoquinone with squaric acid based
methodology leads to furaquinocin E. The use of differentially substituted squaric acid derivatives allows
the synthesis of three analogues of furaquinocin E. The additional stereocenters in furaquinocin A and B
can be introduced with a diastereoselective Sakurai allylation. The stereoselective elongation of the side
chain is possible using cross metathesis or ring closing metathesis. The obtained late-stage intermediates
were successfully transformed to furaquinocin A and B.