Formal total synthesis of grahamimycin A1

Synthesis and Absolute Configuration of (−)-Neuchromenin, a Neurotrophic Metabolite ofEupenicillium javanicum var.meloforme, and Its Enantiomer

“…Unfortunately, all our attempts to acylate 6 at the position α to the carbonyl group failed. Accordingly, we turned our attention to the known aldehyde ( R )‐ 8 ,7 whose cross aldol reaction with 6 would afford ( R )‐ 9 . The lithium enolate of 6 was generated by treatment of 6 with lithium diisopropylamide (LDA) in THF, and treated with ( R )‐ 8 at below −60 °C to give crude ( R )‐ 9 .…”

Enantioselective synthesis of the 13-membered macrodiolide bartanol

“…An acid labile protecting group was required for the alcohol and the tetrahydropyranyl derivative was selected. Reduction of the ester 10 with diisobutylaluminium hydride (DIBAL H) in toluene at -78 "C gave the aldehyde 11 in 93% yield which on treatment with e t hoxycar bon ylme t h y lidene( tripheny1)phosphorane in tetrahydrofuran (THF) gave the required trans alkene 12 as the sole product. Saponification of the ester with sodium hydroxide gave the C,-acid 13.…”

Macrolactonizations in the Total Synthesis of Natural Products

“…In 1976 Mitsunobu described a macrolactonization protocol to obtain medium and large macrolactones. This methodology is based on the activation of the seco-acid alcohol using diethyl azodicarboxylate (DEAD) and triphenylphosphine. − Initially, diolides were usually obtained as the major products for medium ring lactones, ,− and the Mitsunobu reaction has long been considered as a selective method to obtain diolides. A modification was introduced by Steglich in 1991 during the synthesis of combrestatin analogues .…”