The application of an alkaline reaction environment and high temperatures guided us to explore the stability of the 2-Se-bases under these rather harsh conditions. In early experiments we noticed significant oxidation of the starting materials 1 and 2 which manifested itself as a loss of substrate and product, as observed by HPLC, as well as discoloration of the reaction mixtures from colorless to red and black (data not shown). To prevent oxidation and deselenation, reducing agents, such as dithiothreitol (DTT) and ascorbic acid, and inert gases like argon and nitrogen have previously been applied in chemical syntheses and redox studies. This led us to examine whether and for how long the stability of the 2-Se-bases can be increased by the application of DTT and/or a nitrogen atmosphere, which appeared compatible with our reaction system. To this end, we incubated 1 and 2 in different buffer systems (glycine/NaOH pH 9, with or without DTT and with or without a nitrogen atmosphere) at 80 °C and analyzed samples at different time points to check for the integrity of the starting material. Without any additives, oxidation products were already detected after 2 h, with most of the Se-base being degraded after 24 h (Figure and). The addition of DTT had a slightly conserving effect, since no oxidation was apparent after 2 h, but significant deselenation was apparent after 4 and 24 h (Figure and S5). In contrast, saturation of the solution with nitrogen almost completely prevented oxidation of 1 and 2, with only minimal oxidation product being detectable after 24 h (Figure and). As expected, combining DTT and nitrogen prevented oxidation completely and conserved the starting material for 24 h (Figure and).