Synthesis of C-Glycosyl Compounds. Part 2. Reactions of Aldonic Acid Lactones with Ethyl Isocyanoacetate


2,3: 5,6-Di-O-Isopropylidene-D-Mannono-1,4-Lactone Reacted with Ethyl Isocyanoacetate and 1,5-Diazabicyclo-[4,3,0]non-5-Ene (DBN) to Give Ethyl 5-[(1S)-1,2:4,5-Di-O-Isopropylidene-D-Arabinitol-1-Yl]oxazole-4-Carboxylate (1), in Contrast with the Products, (E)- and (Z)-Ethyl 3,6-Anhydro-2-Deoxy-2-Formylamino-4,5:7,8-Di-O-Isopropylidene-D-Manno-Oct-2- Enonate, Obtained When Potassium Hydride Was Used as the Base. Similarly, 2,3:5,6-Di-O-Isopropylidene-D-Allono-1,4-Lactone Gave the Oxazole (9) and the Oct-2-Enonates [(15) and (16)]. Respectively, When DBN and Potassium Hydride Were Used as the Base. with DBN as the Base, 2,3-O-Isopropylidene-4-O-Methyl-L-Rhamnono-1,5-Lactone (20) Gave the Oxazole (21) in Low Yield, and with Potassium Hydride as the Base Both the Oxazole (21) and Anoct-2-Enonate (23) Were Obtained in Low Yield. the Reaction with 2,3,4,6-Tetra-O-Benzyl-D-Glucono-1,5-Lactone and with Potassium Hydride as the Base Gave the Oxazole (27) as the Major Product But No Oct-2-Enonates. with DBN as the Base, Elimination Occurred and Only the Unsaturated Lactone (24) Was Identified. Similarly, 5,6-Di-O-Isopropylidene-2,3-Di-O-Methyl-L-Erythro-Hex-2-Enono-1,4-Lactone Gave Only Elimination Products, the Lactones (33) and (34), When Either of the Two Bases Was Used. the Oxazoles (1), (9), (21), and (27) Were Converted into a Series of Derivatives by a Sequence of Acetylation, Hydrolysis, and Hydrogenolysis Experiments. the Reaction Mechanism Whereby the Oxazoles and Oct-2-Enonates Are Produced is Discussed Briefly.


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Publication Date

01 Jan 1977