The synthesis of complete carbocyclic framework present in bioactive natural products echinothiophene and echinothiophenegenol has been achieved. An acid catalysed rearrangement of isobenzofurans to angularly fused phthalides has been employed as the key step. To the best of our knowledge, this is the first synthetic approach either for the total synthesis or for the partial synthesis of the thieno[2,3-e]isobenzofuran-8(6H)-one framework of the echinothiophene. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim