Studies in Macrolide Synthesis: A Stereocontrolled Synthesis of Oleandolide Employing Reagent- and Substrate-Controlled Aldol Reactions of (S)-1-(Benzyloxy)-2-methylpentan-3-one

Macrocyclization Reactions: The Importance of Conformational, Configurational, and Template-Induced Preorganization

“…Synthesis of the erythromycin core. 383 It is worth mentioning that although the presence of chiral centers can significantly contribute to properly achieving the appropriate conformation of the precursor for the macrocyclization, the exact configuration of the chiral centers is not always a factor determining the success or the failure of the macrocyclization. Diederich and co-workers have prepared different alleno−acetylenic macrocycles (a representative example is depicted in Figure 111, 371) by oxidative homocoupling of optically active and racemic 1,3-diethynylallenes under high dilution conditions.…”

Polypropionate Synthesis via Substrate‐Controlled Stereoselective Aldol Couplings of Chiral Fragments

“…Similar although the silyl ethers 20c,d give slightly lower selectivities. This powerful approach has been successfully applied in the synthesis of several natural products, including muamvatin [77], oleandolide [78], swinholide [79], denticulatins A and B [80] Table 6.3). Considering the relative topicities and enolate diastereoface selectivities for aldol reactions of 21a (Scheme 6.14) and the aldehyde diastereoface selectivities expected for 18 (Schemes 6.8-6.11; Tables 6.1 and 6.2), the multiplicativity rule predicts that aldol reactions of (E)-enol dicyclohexylborinates (S,E)-23 with (R)-18 will be ''matched'' to produce 1,3-anti-1,1 -anti-1 , 2 -syn products 24aas with enhanced stereoselectivity; reactions of (R,E)-23 [ML n = B(c-Hex) 2 ] with (S)-18 will also be ''matched'' to produce ent-24aas.…”

On the Origin of Siphonariid Polypropionates: Total Synthesis of Caloundrin B and Its Isomerization to Siphonarin B

“…8 The preparation of the keto fragment 26 started with the synthesis of ketone 24 (≥97% ee) from the (R)-Roche ester in 59% yield over 3 steps. 21 A boron mediated aldol reaction of 24 with propionaldehyde followed by an in situ syn reduction provided diol 25…”