Having two pure diastereomers (exo,exo and exo,endo) of diester 2 in hands, we tested both in the lithia on/I2-mediated oxida on sequence where the desired stellane deriva ve 1 was formed in near to quan ta ve yield (Scheme 4). The structure of compound 1 was confirmed by XRD crystallography (SI). Analysis of the experimentally measured (XRD) geometry parameters for stellane-1,5-dicarboxylic acid 11 and phtalic acid revealed that stellane core possesses a highly suitable geometry for ortho-subs tuted benzene mimics (Scheme 4). We thus disclosed the dis nct behavior of the diastereomers of compound 2 in the lithia on/I2-mediated oxida on reac ons where endo,endo isomer gives compound 8 through Claisen condensa on (Schemes 1 and 2), whereas exo,exo and exo,endo isomers form stellane deriva ve. In the case of the exo,exo isomer, deprotona on gives rise to a possible enolate I3, which is geometrically unsuitable for intramolecular Claisen cycliza on (Scheme 4). For the exo,endo isomer, there are two possible enolates that can form: enolate I1 and enolate I3. The enolate I1 is formed by abstrac ng a proton marked in red, while enolate I3 is formed by abstrac ng a proton marked in blue. However, when we consider that compound 8 is not observed as a product from exo,endo isomer 2, it suggests that removing the red proton is kine cally unfavorable due to more significant sterical hindrance.