Targe ng stellane 1,5-dicarboxylic acid deriva ves we studied the behavior of other diastereomers of compound 2 in the lithia on/I2-mediated oxida on. For the synthesis of the exo,exo isomer, we used ketone 3 whose reduc on at low temperature with NaBH4 in MeOH provided the corresponding diole 9 as an inseparable mixture of endo,endo and exo,endo isomers in a ra o of ca. 8:1. The tosyla on of the mixture gave a mixture, which could be easily separated by column chromatography, affording the major stereoisomer 10 in a prepara ve yield of 53% (Scheme 3). The SN2-type cyana on of the tosylate 10 with KCN in DMSO gave dinitrile 6 exo,exo with a prepara ve yield of 15%. Acid-mediated hydrolysis of 6 exo,exo yielded the 7 exo,exo diacid, the structure of which was confirmed by XRD crystallography (see SI for details). Analogously to endo,endo dinitrile 6 was converted to the desired diester 2 exo,exo (Scheme 3). Scheme 3. Prepara on of diastereomeric 2 exo,exo and 2 exo,endo diesters.