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Synthesis of the Spiroiminal Moiety of Marineosins A and B

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journal contribution
posted on 02.04.2010, 00:00 by Xiao-Chuan Cai, Xiaoxing Wu, Barry B. Snider
A model for the spiroiminal moiety of marineosins A and B was prepared starting from methylvalerolactone. Addition of vinylmagnesium bromide, protection of the alcohol, and reaction of the vinyl ketone with a protected pyrrole-2-carbonitrile N-oxide gave an isoxazoline. Hydrogenolysis of the N−O bond with Raney nickel gave a keto imine that cyclized to a hemi-iminal. O-Methylation, acid-catalyzed cleavage of the TES group and spiroiminal formation, and deprotection completed a seven-step synthesis.