Diastereoselective Michael–Claisen Cyclizations of γ‑Oxa-α,β-unsaturated Ketones en Route to 5‑Oxatetracyclines

5-Oxatetracyclines were synthesized from d-arabinose using sequential Michael–Claisen cyclization reactions via a 5-oxa-AB enone substrate. The 5-oxatetracyclines were found to have poor stability in aqueous buffer (pH 7.4, 37 °C) and showed little to no inhibition of bacterial growth (S. aureus, E. coli).