Total Synthesis of ( )-Trachyspic Acid 19-n-Butyl Ester
Alex A Rafaniello, Mark A Rizzacasa
ORGANIC LETTERS | AMER CHEMICAL SOC | Published : 2020
The first total synthesis of the alkyl citrate trachyspic acid 19-n-butyl ester (1) is described. A formal [2 + 2]-cycloaddition of the silylketene acetal derived from lactone 6 with di-n-butylacetylene dicarboxylate 7 provided the cyclobutene diester 5 with a dr >20:1. Acid-mediated rearrangement of 5 followed by lactone ring-opening and ester protecting group manipulation eventually provided orthogonally protected aldehyde 3. A Nozaki-Hiyama-Kishi coupling between 3 and vinyl iodide 4 followed by oxidation of the resultant allylic alcohol gave enone 16, which was converted into the triester 17 (dr 6:1) by a spirocyclization/oxidative cleavage/elimination sequence. Removal of the t-butyl es..View full abstract
We thank the Australian Research Council Discovery Program and the University of Melbourne Faculty of Science Research Grant Support Scheme for funding. We also thank Dr. Christian Gunawan and Tony Duncan (Circa Pty Ltd) for the generous gift of (S)-(+)-gamma-hydroxymethyl-gamma-butyrolactone.