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. Author manuscript; available in PMC: 2021 Jun 22.
Published in final edited form as: Nat Chem. 2020 Dec 22;13(1):47–55. doi: 10.1038/s41557-020-00601-1

Fig. 4. Final coupling of tetronic acid derivatives.

Fig. 4

Mild conditions were developed for effecting the coupling of unprotected 5-(halo)methylidene tetronates to carboxylic acids 26 or 27. The structures of HL201 (6), HL204 (29, see Supplementary Information) and HL160 (31), all as the sodium salts, were solved by X-ray diffraction. TMSE = 2-(trimethylsilyl)ethyl, TBAF = tetrabutylammonium fluoride, DMF = N,N-dimethylformamide, DCC = N,N’-dicyclohexylcarbodiimide, DMAP = 4-dimethylaminopyridine, rt = room temperature, HPLC = high pressure liquid chromatography.