In the previous section we demonstrated that our methodology enabled the chemoselective enzymatic acylation of the primary allyl alcohol group in DHLc. Utilizing various aliphatic esters as acyl donors, we managed to achieve very high conversion rates. Given that lactucin (Lc) shares similar structural characteristics to DHLc, except from the presence of an α-methylene-gamma lactone moiety (α-MGL), and considering its abundance as a STL in chicory, we wondered whether we could esterify its primary alcohol via the same approach employed for DHLc. For this experiment we selected vinyl acetate as the acyl donor as it showed complete conversion with DHLc, identical conditions as described in the previous section were applied. The 1 H NMR analysis of the reaction mixture after 48 h showed the expected results: a 100 % conversion and a perfect selectivity towards the primary alcohol. Moreover, the α-MGL moiety remained unchanged as shown in the 1 H NMR spectra ( Building upon these promising results and aiming to extend this concept to encompass the majority of STLs found in chicory root, we ultimately replicated the previous experiment with lactucopicrin (Lp) and 11β,13-dihydrolactucopicrin (DHLp). These two molecules correspond to the ester analogues of Lc and DHLc, respectively, formed at their secondary alcohol sites with 4-hydroxyphenylacetic acid. The high selectivity exhibited by Novozym 435 was of significant interest to us in this instance, as it raised the prospect of selective esterification of the primary alcohol, without the risk of transesterifying the pre-existing ester of these two substrates. Additionally, we aimed to assess the feasibility of the reaction, given that both derivatives are substantially bulkier than the previous substrates due to their additional aromatic ester groups. Adhering to the same conditions used for the reaction between Lc and vinyl acetate, once again we observed 100 % conversion and complete chemoselectivity towards the primary alcohol group. Molecular docking simulations (detailed in the next section) led to 12 % and 22 % of the poses with the primary alcohol function at a distance below 4 Å from the acyl-enzyme carbonyl function in the case of Lc and Lp, respectively. This correlates with high conversion rates of theses substrates despite their bulkier structure compared to Lc and DHLc. To confirm the formation of the desired product, we also performed the LC-MS analysis of lactucopicrin acetate (Lp-Ac) and 11β,13-dihydrolactucopicrin acetate (DHLp-Ac) in addition to NMR analysis. A main peak could be detected in each case, in both positive Due to the challenging extraction process and high cost of Lc, DHLc, Lp, and DHLp, our stock of these compounds was extremely limited. Consequently, we were unable to test the breadth of substrates that we had previously employed with DHLc. However, considering the identical conversion achieved with the four STLs and vinyl acetate, we anticipate that the conversions attainable with the other acyl donors will likely align with those observed for DHLc. This expectation is partly based on the fact that these lipase-catalysed transesterification reactions proceed via the same general mechanism. Still, it is not impossible that the introduction of a bulky group such as 4-hydroxyphenylacetic acid on the secondary alcohol would prevent Lp and DHLp from properly penetrating the active site if it already contained a long aliphatic acyl-enzyme chain. Consequently, these experiments will form the next step of our study, in which we will also evaluate other acyl donors. This will allow us to further increase the range of semi-synthetic STL esters that can be obtained, hoping to help expand the scope of STL research.