The coupling reaction between a carboxylic acid and an alcohol to generate an ester needs a carbodiimide coupling agent. in the reference, the authors report the use of EDCI to prepare compound 1. I have used the same procedure in the synthesis of 1 though not the pure exo isomer but a mixture of exo and endo. In my synthesis I used DIC, a carbodiimide coupling agent that is a liquid at room temperature as opposed to EDCI which is a solid at room temperature. The reaction was run under nitrogen and so the use of DIC allows dropwise addition via a syringe to a sealed mixture of the carboxylic acid and the alcohol. Keeping the reaction dry and inert is important as the resulting ester can otherwise hydrolyze.
The protocol is reprodicible as a 90 % yield was obtained after purification in agreement with the reported yield of 80 %