Starting from the MLPCN probe compound ML300, a structure-based optimization campaign was initiated against the recent severe acute respiratory syndrome coronavirus (SARS-CoV-2) main protease (3CL pro ). X-ray structures of SARS-CoV-1 and SARS-CoV-2 3CL pro enzymes in complex with multiple ML300-based inhibitors, including the original probe ML300, were obtained and proved instrumental in guiding chemistry toward probe compound 41 (CCF0058981). The disclosed inhibitors utilize a noncovalent mode of action and complex in a noncanonical binding mode not observed by peptidic 3CL pro inhibitors. In vitro DMPK profiling highlights key areas where further optimization in the series is required to obtain useful in vivo probes. Antiviral activity was established using a SARS-CoV-2-infected Vero E6 cell viability assay and a plaque formation assay. Compound 41 demonstrates nanomolar activity in these respective assays, comparable in potency to remdesivir. These findings have implications for antiviral development to combat current and future SARS-like zoonotic coronavirus outbreaks.

We recently proposed 3‐methoxy‐4‐methoxycarbonyl‐1,2‐dioxanes 3 as promising scaffolds enabling access to potential antimalarial drugs. We present here an optimized two‐step synthesis of 3 characterized by high yields, simple work‐up procedures and high diastereoselectivity allowing us to readily prepare 3 on multigram scale. The versatility of the 1,2‐dioxane scaffold was demonstrated by our generation of a new family of 1,2‐dioxane‐4‐carboxamides 8a–h and the realization of their in vitro activities against chloroquine‐sensitive (D10) and chloroquine‐resistant (W2) P. falciparum strains. In particular, one of these amides (8e), displayed antimalarial activity on par with the natural product lead plakortin and was 5‐fold more active than its methyl ester analogue 3. Structure–activity relationship (SAR) analysis supported by DFT calculations revealed that, for this family of compounds, alkyl substituents at C6 dictate, in large part, the degree of antimalarial activity. This finding contrasts those previously observed for the ester series.

A new series of nineteen 3-methoxy-1,2-dioxanes containing an amino moiety at C4 was designed, synthesized and tested for in vitro antimalarial activity against chloroquine sensitive (CQ-S) D10 and chloroquine resistant (CQ-R) W2 strains of Plasmodium falciparum (Pf). Cytotoxicity against the human endothelial cell line (HMEC-1) was also evaluated. The introduced modifications resulted in a notable improvement of the antimalarial activity. In particular, compound 9a with an amino-imidazole side-chain at C4 displays antimalarial activity in the high nanomolar range against the CQ-R Pf strain (W2 IC 50 ¼ 200 nM), being more active against CQ-R than CQ-S Pf strains and devoid of cytotoxicity against human HMEC-1 cells. On the other hand, some of the hybrids with 4-amino-7-chloroquinoline (9k-p) show an IC 50 comparable to that of chloroquine against the CQ-S Pf strain (9k-p, D10 IC 50 ¼ 50-90 nM) but without losing potency against the CQ-R Pf strain (9k-p, resistance index ¼ 1.2-2.6), with low cytotoxicity against HMEC-1. Structure-activity relationship studies show that the improved antimalarial activity of the new compounds is the result of a combination of cellular pharmacokinetics and pharmacodynamics effects.

We report herein a newly developed domino reaction that facilitates the synthesis of new 1,5-dideoxy-1,5-iminoribitol iminosugar C-glycosides 7a-e and 8. The key intermediate in this approach is a six-membered cyclic sugar nitrone that is generated in situ and trapped by an alkene dipolarophile via a [2 + 3] cycloaddition reaction to give the corresponding isooxazolidines 10a-e in a "one-pot" protocol. The iminoribitol C-glycosides 7a-e and 8 were found to be modest β-galactosidase (bGal) inhibitors. However, compounds 7c and 7e showed "pharmacological chaperone" activity for mutant lysosomal bGal activity and facilitated its recovery in GM1 gangliosidosis patient fibroblasts by 2-6-fold.