Enantioselective Syntheses of Heliannuols G and H

Stereoselective Synthesis of Terpenoids through Lipase-Mediated Resolution Approaches

“…These two studies demonstrate that it is possible to obtain both R and S enantiomers of the monoacetate 125 by using PPL or CRL, respectively. These two enantiomers were then employed in a number of studies aimed at stereoselective sesquiterpenes synthesis [102][103][104][105][106]. The example of compound 126 [107] is completely different.…”

An Integrated ANN-PRA/DP4+ Tandem Computational Approach Contributing to the Ordering of the Heliannuol Family

“…31,32,35,36 For heliannuols G and H, as an example, Morimoto et al 31 claimed to have synthesized the supposed proposed structures isolated by Macı ́as et al 8 and emphasized that the 1 H NMR chemical shift data for these molecules are different from isolated natural products. 31 In 2006, Morimoto and collabo-rators suggested a review of the structure of molecules of natural origin in which they proposed a structure that presents an aromatic ring fused to a 5-membered heterocyclic ring (Figure 2). 32 The same happens for another member of this family: heliannuol L. Given the resemblance to NMR data from previously isolated molecules in the same class, Macı ́as and colleagues suggested that the structure of heliannuol L could be consistent with a 7-or 8-membered ether ring, leading to four possible isomers for heliannuol L (Figure 3).…”

“…Biological evaluation has shown that heliannuols yield allelopathic activity and may be used as lead compounds in herbicides, where heliannuols A–K were assessed for their natural herbicidal activities against seed germination and/or growth, as well as coleoptile elongation, targeting dicotyledonous species. − Furthermore, in addition to this interesting biological activity, the heliannuol family has drawn the wide attention of synthetic groups, and the synthesis of this family of molecules has always been challenging due to the unique scaffold and multiple chiral centers. − …”

“…Unfortunately, not all that glitter is gold. It is worth mentioning that, although there is a considerable number of articles describing the total synthesis of heliannuols, several examples of the class do not present any synthetic proposal. − In 2020, Ribeiro et al published a review article in which they compiled the data described in the literature regarding isolation, biological activity, syntheses, and spectral characteristics of 1 H and 13 C NMR for already isolated heliannuols and correlated them with their respective structures . Additionally, the authors described inconsistencies in the family, among which it is noteworthy that in most synthetic cases, the authors did not describe the full NMR data, instead, it only indicates that they were similar to the natural product.…”

“…Additionally, the authors described inconsistencies in the family, among which it is noteworthy that in most synthetic cases, the authors did not describe the full NMR data, instead, it only indicates that they were similar to the natural product. More than that, in many cases, the originally proposed structures of several members of the heliannuol family were based, among other facts, on structural correlations with similar molecules already known in the literature and by the similarity of NMR data of previously isolated molecules, where little or no stereochemical analysis was performed. − , Hence, as a consequence, structural reassignment is a recurring theme in the heliannuol family. ,,, …”