In this vein, we first reduced naphthalene 9 to 1,4-dihydronaphthalene 8, making the outer double bond accessible for the subsequent rhodium(II) catalyzed cyclopropanation , giving cyclopropane 10 as a diastereomeric mixture of trans-10 and cis-10 (2:1). Separation of the two isomers trans-10 and cis-10 was achieved by iterative temperature-dependent saponification with KOH exploiting the innate reactivity difference of the diastereomeric cyclopropyl esters trans-10 and cis-10: a first saponification with KOH at room temperature selectively transformed trans-10 to the trans-11 acid and thus facilitated removal of unwanted trans isomer. Raising the temperature from room temperature to reflux afforded the all-ciscarboxylic acid cis-11 through subsequent saponification under elevated temperature. In allcis-11, the carboxylic acid is aligned suitably towards the benzene ring, a key necessity for the downstream intramolecular Buchner reaction. It should be noted that this particular Buchner reaction is further impeded by the fact that acetoacetate-derived diazo compounds generally display significantly lower reactivity in cyclopropanation reactions . We continued by activation of all-cis-11 and chain elongation by Claisen condensation to form acetoacetate 12.