Lepadins are cis-fused decahydroquinoline (DHQ) marine alkaloids that have shown diverse biological activities and have attracted extensive synthetic interest. A new collective synthetic strategy is reported that features a green chemistry approach for constructing the common cis-fused DHQ core, which is achieved through green oxone-halide oxidation for both the aza-Achmatowicz rearrangement and the intramolecular [3 + 2] cycloaddition of nitrile oxide-alkene. Collective total syntheses of lepadins A-E and H are accomplished from the common DHQ core within 10 steps.