been recently obtained from the pairwise addition of parahydrogen to [1- C]acetylene dicarboxylate, thanks to the use of a trans-hydrogenative Ru-based catalyst (Fig. ) . This represents a significant development, because the most widely used hydrogenative PHIP catalyst (a Rh-based complex) leads to cishydrogenation of substrates, and its use here would lead to toxic maleate being obtained . However, in order to progress to meaningful metabolic application, it is crucial to improve the fumarate polarization level and yield of the hydrogenation reaction.