Total Syntheses of (+)-Aigialospirol and (+)-7′,8′-Dihydroaigialospirol by a One-Pot Stepwise Approach

(+)-Aigialospirol and (+)-7',8'-dihydroaigialospirol are known to be spiroketal polyketide-type natural products isolated from mangrove-derived fungus <i>Aigialus parvus</i> BCC 5311. These polyketides are structurally characterized by fusing resorcylic acid lactone and spiroketal moieties containing six asymmetric carbon centers. In this paper, we describe concise and stereoselective syntheses of these natural products based on biosynthesis-inspired transformation in nine steps. The total syntheses are highlighted by a one-pot stepwise synthesis involving (i) stereoselective lactone ring formation from a chiral epoxide, (ii) reduction of alkyne, (iii) global deprotection, and (iv) spiroketal formation, which are performed in the final step of the total synthesis.