Synthesis of 2-methyl-D-erythritol via epoxy ester-orthoester rearrangement

Catalytic Asymmetric Darzens-Type Epoxidation of Diazoesters: Highly Enantioselective Synthesis of Trisubstituted Epoxides

Highly enantioselective Darzens-type epoxidation of diazoesters with glyoxal derivatives was accomplished using a chiral boron-Lewis acid catalyst, which facilitated asymmetric synthesis of trisubstituted α,β-epoxy esters. In the presence of a chiral oxazaborolidinium ion catalyst, the reaction proceeded in high yield (up to 99 %) with excellent enantio- and diastereoselectivity (up to >99 % ee and >20:1 dr, respectively). The synthetic potential of this method was illustrated by conversion of the products to various compounds such as epoxy γ-butyrolactone, tertiary β-hydroxy ketone and epoxy diester.

Oxetane Intermediate during a Direct Aldol Reaction: Stereoselective [5 + 1] Annulation Affording Tetralines

An oxetane intermediate during a direct aldol reaction was trapped with an internal aryl group to yield trans-tetraline products. The contribution of the oxetane intermediate was confirmed by ¹⁸O-isotope labeling experiments.

Synthesis and Evaluation of Fluoroalkyl Phosphonyl Analogues of 2- C-Methylerythritol Phosphate as Substrates and Inhibitors of IspD from Human Pathogens

Targeting essential bacterial processes beyond cell wall, protein, nucleotide, and folate syntheses holds promise to reveal new antimicrobial agents and expand the potential drugs available for combination therapies. The synthesis of isoprenoid precursors, isopentenyl diphosphate (IDP) and dimethylallyl diphosphate (DMADP), is vital for all organisms; however, humans use the mevalonate pathway for production of IDP/DMADP while many pathogens, including Plasmodium falciparum and Mycobacterium tuberculosis, use the orthogonal methylerythritol phosphate (MEP) pathway. Toward developing novel antimicrobial agents, we have designed and synthesized a series of phosphonyl analogues of MEP and evaluated their abilities to interact with IspD, both as inhibitors of the natural reaction and as antimetabolite alternative substrates that could be processed enzymatically to form stable phosphonyl analogues as potential inhibitors of downstream MEP pathway intermediates. In this compound series, the S-monofluoro MEP analogue displays the most potent inhibitory activity against Escherichia coli IspD and is the best substrate for both the E. coli and P. falciparum IspD orthologues with a K_m approaching that of the natural substrate for the E. coli enzyme. This work represents a first step toward the development of phosphonyl MEP antimetabolites to modulate early isoprenoid biosynthesis in human pathogens.

Total synthesis of (+)-iresin

The first asymmetric total synthesis of (+)-iresin (4), an historically important ent-Drimane sesquiterpene lactone, was realized from aldehyde 3 via cyclic orthoester 6 in 5 steps. Notable transformations in this synthesis include a tandem trifluoroperacetic acid (TFPAA)-mediated Baeyer-Villiger oxidation-olefin epoxidation-epoxy ester cyclization, regioselective Burgess dehydration, and regioselective Fétizon oxidative lactonization.

Alternative synthesis of the Colorado potato beetle pheromone

A concise preparation of the pheromone secreted by the male Colorado potato beetle [viz. (3S)-1,3-dihydroxy-3,7-dimethyl-6-octen-2-one] was accomplished in four steps starting from 2-fluoronerol or 2-fluorogeraniol. The key step in the synthesis involves a 6-endo epoxide ring-opening with ester participation that simultaneously inverts the 3R-configuration of the (3R)-2,3-epoxy-2-fluoroprenyl acetate intermediate and installs the ketone functionality of the semiochemical. Extensive NMR studies validate the proposed 6-endo mechanism of the featured rearrangement, which under anhydrous conditions resulted in the formation of two bicyclic 1,3-dioxan-5-ones via an unprecedented intramolecular Prins cyclization.

Metabonomic investigation of human Schistosoma mansoni infection

Schistosomiasis is a parasitic infection that is endemic in many developing countries in the tropics and subtropics afflicting more than 207 million people primarily in rural areas. After malaria, it is the second most important parasitic infection in terms of socio-economic and public health. Investigation of the host-parasite interaction at the molecular level and identification of biomarkers of infection and infection-related morbidity would be of value for improved strategies for treatment and morbidity control. To this end, we conducted a nuclear magnetic resonance (NMR) based metabonomics study involving a well-characterized cohort of 447 individuals from a rural area in Uganda near Lake Victoria with a high prevalence of Schistosoma mansoni, a species predominantly occurring in Africa including Madagascar and parts of South America. Cohort samples were collected from individuals at five time-points, before and after (one or two times) chemotherapy with praziquantel (PZQ). Using supervised multivariate statistical analysis of the recorded one-dimensional (1D) NMR spectra, we were able to discriminate infected from uninfected individuals in two age groups (children and adults) based on differences in their urinary profiles. The potential molecular markers of S. mansoni infection were found to be primarily linked to changes in gut microflora, energy metabolism and liver function. These findings are in agreement with data from earlier studies on S. mansoni infection in experimental animals and thus provide corroborating evidence for the existence of metabolic response specific for this infection.