ABSTRACT
Presilphiperfolan-8ß-ol synthase (BcBOT2), a substrate-promiscuous sesquiterpene cyclase (STC) of fungal origin, is capable of converting two new farnesyl pyrophosphate (FPP) derivatives modified at C7 of farnesyl pyrophosphate (FPP) bearing either a hydroxymethyl group or a methoxymethyl group. These substrates were chosen based on a computationally generated model. Biotransformations yielded five new oxygenated terpenoids. Remarkably, the formation of one of these tricyclic products can only be explained by a cationically induced migration of the methoxy group, presumably via a Meerwein-salt intermediate, unprecedented in synthetic chemistry and biosynthesis. The results show the great principle and general potential of terpene cyclases for mechanistic studies of unusual cation chemistry and for the creation of new terpene skeletons.
Subject(s)
Sesquiterpenes , Sesquiterpenes/chemistry , Sesquiterpenes/metabolism , Polyisoprenyl Phosphates/chemistry , Polyisoprenyl Phosphates/metabolismABSTRACT
Targeted protein degradation (TPD) and proteolysis-targeting chimeras (PROTACs) have arisen as powerful therapeutic modalities for degrading specific proteins in a proteasome-dependent manner. However, a major limitation of TPD is the lack of E3 ligase recruiters. Recently, we discovered the natural product nimbolide as a covalent recruiter for the E3 ligase RNF114. Here, we show the broader utility of nimbolide as an E3 ligase recruiter for TPD applications. We demonstrate that a PROTAC linking nimbolide to the kinase and BCR-ABL fusion oncogene inhibitor dasatinib, BT1, selectively degrades BCR-ABL over c-ABL in leukemia cancer cells, compared to previously reported cereblon or VHL-recruiting BCR-ABL degraders that show opposite selectivity or, in some cases, inactivity. Thus, we further establish nimbolide as an additional general E3 ligase recruiter for PROTACs, and we demonstrate the importance of expanding upon the arsenal of E3 ligase recruiters, as such molecules confer differing selectivity for the degradation of neo-substrate proteins.
Subject(s)
Fusion Proteins, bcr-abl/antagonists & inhibitors , Limonins/pharmacology , Protein Kinase Inhibitors/pharmacology , Proteolysis/drug effects , Thiazoles/pharmacology , Fusion Proteins, bcr-abl/chemistry , Fusion Proteins, bcr-abl/metabolism , Humans , K562 Cells , Limonins/chemistry , Protein Kinase Inhibitors/chemistry , Thiazoles/chemistry , Ubiquitin-Protein Ligases/metabolismABSTRACT
An improved scalable synthesis of orthogonally functionalized methoxyaspartate, the chiral hinge region element in cystobactamids, is reported. This improvement sets the stage for the total synthesis of four new cystobactamids along with cystobactamid 861-2, whose antibacterial properties are determined and compared. The cyano derivative of cystobactamide 861-2 shows superior antibacterial activity against Gram-negative bacteria to any natural cystobactamide tested so far.
