Towards the total synthesis of clerocidin. Efficient assembly of the decalin subunit

Synthesis of Clerodane Diterpenoids and Related Compounds - Stereoselective Construction of the Decalin Skeleton with Multiple Contiguous Stereogenic Centers

“…In an investigation of a similar aim, Markó reported very recently that the catalytic hydrogenation of methylene derivative 64b in the presence of Ir-black proceeded preferentially for the formation of 8,9trans-epimer 65b in a ratio of 87: 13 (Scheme 8). 62 Further conversion of 65b led to the synthesis of an intermediate 66b. Kobayashi reported recently in connection with synthetic studies on akaterpin 67, a specific inhibitor of phosphatidylinositol phospholipase, that the hydrogenation of methylene compound 68 in the presence of Raney Ni showed a stereoselectivity of 8,9-trans/cis = 1: 2.1.…”

Unexpected Racemization in the Course of the Acetalization of (+)-(S)-5-Methyl-Wieland–Miescher Ketone with 1,2-Ethanediol and TsOH under Classical Experimental Conditions

“…In the course of our work on bioactive natural products and bioactive materials [117][118][119][120][121][122][123][124], it occurred to us to observe the partial racemization of (+)-5 during the acetalization of (+)-1 with 1,2-ethanediol and TsOH in the presence of a Dean-Stark apparatus. According to our best knowledge, obtaining partially racemized (+)-5 or (−)-5 when the acetalization reaction is carried out by this procedure on (+)-1 or (-)-1 [33,35,39,40,44,48,49,72,77,81,84,[87][88][89][90][91]116], respectively, has not been previously reported in the literature, which was the reason behind investigating this reaction.…”