Hydrolysis iminoether

Nagata s method. Reduction of the ketone with sodium borohydride stereoselec-tively led to the alcohol, which on repeated chromatography on basic alumina cyclized to the iminoether, 165. Its conversion into 14-oxodendrobine (97) was achieved by tosylation to the tosylamide and subsequent basic hydrolysis. The authors developed an alternative route from cyanoketone 164 to 14-oxodendrobine (97) by hydrolyzing the nitrile under acidic conditions. The acid formed was esterified with diazomethane and the ketone 166 was reduced stereoselectively with sodium borohydride. Subsequent saponification and acidic lactonization led to 14-oxodendrobine (97). Inubushi et al. also used Borch s method to convert 14-oxodendrobine (97) into dendrobine (82) via the lactimether 167 and reduction. 

The chemical synthesis of 7-ACA (Fig. 3) is a classical organic route, which uses equimolar amounts of chemicals. A preferred process is the so-called iminoha-lide/iminoether deacylation route, involving formation of the iminochloride by reaction with PCI5, conversion into the iminoether by treatment with alcohol and hydrolysis with water [7]. Highly purified cephalosporin C, isolated, for example as the zinc salt, is required as a dried solid as the starting material. 

Saegusa et al. invented a new method of preparing linear polyEI67). This method involves the izomerization polymerization of cyclic iminoethers (cf. Chap. 12), followed by alkaline hydrolysis, leading to perfectly linear crystalline polymers. Using oxazoline (x = 2) and oxazine (x = 3), polyEI and poly(trimethyleneamine) were prepared ... 

The parent member of this class of compounds, l,4-dioxepan-5-one, and its methyl derivatives (119) have been prepared by Baeyer-Villiger oxidation, and the methyl derivative has been transformed to the dioxepinone (121) <89MM3838,94CC687>. l,4-Dioxepan-5-one could also be obtained by cyclization of (122) and hydrolysis of the intermediate iminoether hydrochloride (123) (Scheme 11) <89MM3838>. 

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