Stereoselective total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone via asymmetric acetate aldol reaction

Stereoselective total synthesis of (-)-(6S,2'R)-cryptocaryalactone

We described a novel stereoselective total synthesis of (-)-(6S,2'R)-cryptocaryalactone, a natural product containing syn/anti-6,8-diol/5,6-dihydro-2H-pyran-2-one unit. The approach, which characterised a highly diastereoselective chelation-controlled Mukaiyama aldol reaction of a benzyl-protected aldehyde and a Yamaguchi lactonisation of a δ-hydroxy-trans-α,β-unsaturated carboxylic acid, is an alternative synthetic strategy towards cryptocaryalactones.

Synthesis and determination of absolute configuration of α-pyrones isolated from Penicillium corylophilum

The first total synthesis of (S)-6-(2,9-dihydroxynonyl)-4-hydroxy-3-methyl-2H-pyran-2-one, 4-hydroxy-3-methyl-6-((2S,4R)-2,4,11-trihydroxyundecyl)-2H-pyran-2-one, and its unnatural 2R,4R-isomer starting from commercially available 1,8-octanediol is described. The synthesis led to the revision of the proposed structural assignment of the natural product as (R)-6-(2,9-dihydroxynonyl)-4-hydroxy-3-methyl-2H-pyran-2-one. The key steps include chiral auxiliary mediated asymmetric acetate aldol reaction, dianion addition, and base mediated cyclization to form an α-pyrone ring.