337359-83-8Relevant academic research and scientific papers
Radical oxidative cyclization of spiroacetals to bis-spiroacetals: An overview
Brimble, Margaret A.
, p. 394 - 404 (2004)
The use of iodobenzene diacetate and iodine under photolytic conditions provides and efficient method for the oxidative cyclization of spiroacetals bearing an hydroxyalkyl side chain to bis-spiroacetals. An overview is provided of the use of this reaction
Synthesis of the bis-spiroacetal moiety of the polyether antibiotic CP44,161
Allen, Paul R.,Brimble, Margaret A.,Prabaharan, Hishani
, p. 379 - 389 (2007/10/03)
The syntheses of bis-spiroacetals 25a, 25c and 40 which constitute the central framework of the polyether antibiotic CP44,161 4, are described. The tricyclic bis-spiroacetal ring is formed by oxidative cyclisation of hydroxyspiroacetal 9 which in turn is assembled from lactone 10 and acetylene 11. The key stereogenic centres in acetylene 11 were assembled using a Sharpless asymmetric dihydroxylation and an Evans asymmetric alkylation of a chiral oxazolidinone. Asymmetric dihydroxylation of alkene 14 using (DHQ)2PHAL (hydroquinine phthalazine-1,4-diyl diether) led to acetylene 22 which in turn was converted to bis-spiroacetals 25a and 25c. Construction of the isomeric acetylene 11 was effected via Sharpless asymmetric dihydroxylation of alkene 14 using the pseudoenantiomeric chiral ligand (DHQD)2PHAL which in turn led to the formation of bis-spiroacetal 40 with the same configuration at C-2 as that present in antibiotic CP44,161 4. Barbier addition of bromide 8 to bisspiroacetal aldehyde 27 afforded alcohol 28 which was then converted to polyethers 32 and 33 via an epoxidation cyclization strategy. This latter reaction sequence demonstrated the feasibility of appending the E ring to the tricyclic bis-spiroacetal BCD ring system of antibiotic CP44,161 4.
