Total Synthesis and Correct Absolute Configuration of Malyngamide U

The enantioselective synthesis of the previously proposed structure of malyngamide U (1) was
accomplished in 18 steps from (S)-(+)-carvone. The key steps involved a hydroxymethylation of (S)-(+)-carvone and an asymmetric Henry reaction of aldehyde (+)-5, as well as condensation with the acid
3. The 1H and 13C NMR data of the synthetic compound 1 were not consistent with the data of the
reported malyngamide U. The C-2‘ epimer of compound 1 was therefore synthesized by a similar reaction
sequence. While the NMR data of C-2‘ epimer 23 were in full agreement with those of the reported
product, the discrepancy in the specific rotation data suggested the correct structure of malyngamide U
should be structure 2, in which the absolute configuration of the amine part was enantiomeric with that
in compound 23. Then the correct absolute configuration of revised malyngamide U (2) was confirmed
by the similar synthesis from (R)-(-)-carvone.