In this paper, we describe the structure-based design, synthesis, and biological evaluation of cytosine derivatives and analogues that inhibit IspF, an enzyme in the non-mevalonate pathway of isoprenoid biosynthesis. This pathway is responsible for the biosynthesis of the C 5 precursors to isoprenoids, isopentenyl diphosphate (IPP, 1) and dimethylallyl diphosphate (DMAPP, 2; Scheme 1). The nonmevalonate pathway is the sole source for 1 and 2 in the protozoan Plasmodium parasites. Since mammals exclusively utilize the alternative mevalonate pathway, the enzymes of the non-mevalonate pathway have been identified as attractive new drug targets in the fight against malaria. Based on computer modeling (cf. Figs. 2 and 3), new cytosine derivatives and analogues (Fig. 1) were selected as potential drug-like inhibitors of IspF protein, and synthesized (Schemes 2 -5). Determination of the enzyme activity by 13 C-NMR spectroscopy in the presence of the new ligands showed inhibitory activities for some of the prepared cytosine and pyridine-2,5-diamine derivatives in the upper micromolar range (IC 50 values; Table). The data suggest that it is possible to inhibit IspF protein without binding to the polar diphosphate binding site and the side chain of Asp56', which interacts with the ribose moiety of the substrate and substrate analogues. Furthermore, a new spacious sub-pocket was discovered which accommodates aromatic spacers between cytosine derivatives or analogues (binding to Pocket III ) and rings that occupy the flexible hydrophobic region of Pocket II . The proposed binding mode remains to be further validated by X-ray crystallography.

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In this paper, we describe the synthesis and biological evaluation of highly substituted perhydropyrrolizines that inhibit the peptidyl-prolyl cis/trans isomerase (PPIase) Pin1, an oncogenic target. The enzyme selectively catalyzes the cis/trans isomerization of peptide bonds between a phosphorylated serine or threonine, and proline, thereby inducing a conformational change. Such structural modifications play an important role in many cellular events, such as cell-cycle progression, transcriptional regulation, RNA processing, as well as cell proliferation and differentiation. Based on computer modeling (Fig. 2), the new perhydropyrrolizinone derivatives (À)-1a,b, decorated with two substituents, were selected and synthesized (Schemes 1 -3). While enzymatic assays showed no biological activity, 15 N, 1 H-HSQC-NMR spectroscopy revealed that (À)-1a,b bind to the WW recognition domain of Pin1, apparently in a mode that does not inhibit PPIase activity. To enforce complexation into the larger active site rather than into the tighter WW domain of Pin1 and to enhance the overall binding affinity, we designed a perhydropyrrolizine scaffold substituted with additional aromatic residues (Fig. 5). A novel, straightforward synthesis towards this class of compounds was developed (Schemes 4 and 5), and the racemic compounds (AE)-22a -22d were found to inhibit Pin1 with K i values (K i = inhibition constant) in the micromolar range ( Table 2). To further enhance the potency of these inhibitors, the optically pure ligands (+)-22a and (+)-33b,c were prepared (Schemes 6 and 7) and shown to inhibit Pin1 with K i values down to the single-digit micromolar range. According to 15 N, 1 H-HSQC-NMR spectroscopy and enzymatic activity assays, binding occurs at both the WW domain and the active site of Pin1. Furthermore, the new synthetic protocol towards perhydropyrrolizines was extended to the preparation of highly substituted perhydroindolizine ((AE)-43; Scheme 8) and pyrrolidine ((AE)-48a,b; Scheme 9) derivatives, illustrating a new, potentially general access to these highly substituted heterocycles.

We report a short synthetic route that provides optically active 2-substituted hexahydro-1H-pyrrolizin-3-ones in four steps from commercially available Boc (tert-but(oxy)carbonyl))-protected proline. Diastereoisomers (À)-11 and (À)-12 were assembled from the proline-derived aldehyde (À)-8 and ylide 9 via a Wittig reaction and subsequent catalytic hydrogenation (Scheme 3). Cleavage of the Boc protecting group under acidic conditions, followed by intramolecular cyclization, afforded the desired hexahydro-1H-pyrrolizinones (À)-1 and ()-13. Applying the same protocol to ylide 19 afforded hexahydro-1H-pyrrolizinones (À)-25 and (À)-26 (Scheme 5). The absolute configuration of the target compounds was determined by a combination of NMR studies ( Figs. 1 and 2) and X-ray crystallographic analysis (Fig. 3).

To support perfumers in their creation of olfactive signatures resulting in unique and instantly recognizable perfumes, there is a constant demand for the development of new odorant molecules and of novel processes for their production. Increasing the sustainability of both the molecules and the processes is a crucial activity at Givaudan. Biocatalysis has the potential to positively influence metrics applied at Givaudan that drive and measure our ambition to innovate responsibly, which is summarized in the FiveCarbon Path™. It targets an increased use of renewable carbon, carbon efficiency in synthesis, and the production of powerful and biodegradable odorant molecules while maximizing the use of upcycled carbon available from waste and side streams. This review illustrates with some examples how enzymes selected from the oxidoreductase and isomerase enzyme classes are applied at Givaudan for the preparation of odorant molecules both at laboratory and industrial scale.