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Tetraallylsilane can undergo either a mono or double rearrangement when treated with iodine (I2). The extent of rearrangement depends on the equivalents of I2 used, where 1 equivalent gives high yields of mono-rearranged products and excess (e.g., 3 equivalents) causes double rearrangement to occur. This transformation can be applied to the synthesis of potentially valuable silicon-stereogenic organosilanes.

Polyunsaturated long-chain alkenones are a unique class of lipids biosynthesized in significant quantities (up to 20% of cell carbon) by several algae including the industrially grown marine microalgae Isochrysis . Alkenone structures are characterized by a long linear carbon chain (35–40 carbons) with one to four trans double bonds and terminating in a methyl or ethyl ketone. Alkenones were extracted and isolated from commercially obtained Isochrysis biomass and then subjected to cross-metathesis (CM) with methyl acrylate or acrylic acid using the Hoveyda–Grubbs metathesis initiator. Within 1 h at room temperature alkenones were consumed; however, complete fragmentation (i.e., conversion to the smallest subunits by double bond cleavage) required up to 16 h. Analysis of the reaction mixture by gas chromatography and comprehensive two-dimensional gas chromatography revealed a predictable product mixture consisting primarily of long-chain (mostly C 17 ) acids (or methyl esters from CM with methyl acrylate) and diacids (or diesters), along with smaller amounts (~5%) of the honey bee “queen substance” ( E )-9-oxo-decenoic acid. Together, these compounds comprise a diverse mixture of valuable chemicals that includes surfactants, monomers, and an agriculturally relevant bee pheromone.

Sun exposure can affect the skin in various ways leading to short- and long-term consequences. Waxes are often used to optimize the rheological behavior of products and provide an even sunscreen film on the skin, which can boost the sun protection factor (SPF) of ultraviolet (UV) filters. In this study, a biobased wax, alkenones, sourced from commercially available and sustainable microalgae was evaluated as an SPF booster in sunscreens. Thirty-five sunscreens were formulated using three waxes and four organic liquid UV filters. Products were tested for pH, viscosity, spreadability, stability, as well as in vitro SPF and water resistance. Alkenones’ in vitro SPF boosting capacity was similar to beeswax and cetyl alcohol with three “reef-safe” UV filters. None of the waxes used provided significant water resistance, however, using film-former water resistance could be built into the products. A key finding is that alkenones increased the in vitro SPF without increasing apparent viscosity. All products had a skin-compatible pH and they all remained stable at 25 °C for 10 weeks. Overall, the alkenones’ performance was comparable to those of the comparator waxes. Our in vitro results indicate that alkenones offer a sustainable, biobased, non-animal derived choice as an SPF booster for organic sunscreens.

The move toward green, sustainable, natural products has been growing in the cosmetic and personal care industry. Ingredients derived from marine organisms and algae are present in many cosmetic products. In this study, a new green ingredient, a wax (i.e., long-chain alkenones) derived from Isochyrsis sp., was evaluated as an alternative for cosmetic waxes. First, the melting point was determined (71.1–77.4 °C), then the alkenones’ thickening capability in five emollients was evaluated and compared to microcrystalline wax and ozokerite. Alkenones were compatible with three emollients and thickened the emollients similarly to the other waxes. Then, lipsticks and lip balms were formulated with and without alkenones. All products remained stable at room temperature for 10 weeks. Lipstick formulated with alkenones was the most resistant to high temperature. Finally, alkenones were compared to three cosmetic thickening waxes in creams. Viscosity, rheology, and stability of the creams were evaluated. All creams had a gel-like behavior. Both viscosity and storage modulus increased in the same order: cream with alkenones < cetyl alcohol < stearic acid < glyceryl monostearate. Overall, alkenones’ performance was comparable to the other three waxes. Alkenones can thus offer a potential green choice as a new cosmetic structuring agent.

Background In malaria-endemic countries, large proportions of infected individuals are asymptomatic, constituting a reservoir of parasites for infection of newly hatched mosquitoes. This study evaluated the impact of screening and treatment of asymptomatic carriers of Plasmodium falciparum . Methods Eighteen villages were randomized (1:1) to study arms and inhabitants participated in four community screening campaigns: three before the rainy season ~1 month apart, and the fourth after the rains at ~12 months. On day 1 of campaigns 1–3, asymptomatic carriers in the intervention arm were identified by rapid diagnostic test and treated with artemether-lumefantrine. Outcomes were symptomatic malaria with parasite density >5,000/μL per person-year in children <5 years and change in haemoglobin between days 1 and 28 of campaign 1. Results At 12 months, the number of symptomatic malaria episodes with a parasite density >5,000/μL per person-year in children <5 years was not significantly different between arms (1.69 vs 1.60, p = 0.3482). Mean haemoglobin change in asymptomatic carriers during campaign 1 was greater in the intervention vs control arm (+0.53 g/dL vs -0.21 g/dL, p <0.0001). ANCOVA demonstrated that mean asymptomatic carriage at the cluster level was lower in the intervention vs control arm at day 1 of campaigns 2 (5.0% vs 34.9%, p <0.0001) and 3 (3.5% vs 31.5%, p <0.0001), but showed only a small difference at day 1 of campaign 4 (34.6% vs 37.6%, p = 0.2982). Mean gametocyte carriage was lower in the intervention vs control arm at day 1 of campaigns 2 and 3 (0.7% vs 5.4%, p <0.0001; 0.5% vs 5.8%, p <0.0001), but was similar at day 1 of campaign 4 (4.9% vs 5.1%, p = 0.7208). Conclusions Systematic screening and treatment of asymptomatic carriers at the community level did not reduce clinical malaria incidence in the subsequent transmission season, indicating greater levels of parasite clearance are required to achieve a sustained impact in this setting.

The U.S. Virgin Islands (USVI) has a rich fishing history that remains integral to both its culture and economy, with species like yellowtail snapper (Ocyurus chrysurus) being particularly valuable and sought after. Ecologically, yellowtail snapper play a key role as carnivorous predators with diverse feeding habits, consuming a range of prey such as fish, crustaceans, and zooplankton. During their juvenile phase, yellowtail snappers rely on seagrass beds as nursery habitats, which provide essential resources like food and shelter. In 2002, the invasive seagrass Halophila stipulacea was first observed in the Caribbean and has since spread across the region, displacing native seagrass species. This study compared the growth, diet, and foraging behavior of juvenile yellowtail snapper in both native and invasive seagrass beds. Zooplankton collections in native and invasive seagrass beds and gut content analysis of juvenile yellowtail snapper revealed that juveniles consumed a similar diversity of prey items, though they may be exposed to higher copepod abundance but fewer larger prey items in the invasive seagrass. Foraging behavior showed juveniles in H. stipulacea exhibited smaller feeding ranges compared to those in native seagrasses, although they bit at the same frequency in both habitats. Otolith growth ring analysis indicated that juvenile yellowtail snapper grew at similar rates among all seagrass species. These findings suggest that the invasive seagrass may have minimal impact on yellowtail snapper, potentially fulfilling a similar nursery role as native seagrasses.

This chapter focuses on cross‐metathesis applications and surveys the literature between 2003 and 2013, highlighting examples from more than 480 papers. After a brief historical overview of cross‐metathesis reactions using well‐defined molybdenum and ruthenium catalysts, olefin functionalization reactions are presented by the group on the smaller or more readily available coupling partner. Functional groups are arranged by their defining element and appear in the order of carbon, boron, nitrogen, oxygen, halides, sulfur, and phosphorus. Examples include alkane extensions, unsaturated hydrocarbons such as styrene and ethylene, vinyl boronates, amines, acrylonitrile, allylic and homoallylic alcohols, vinyl ethers, acrolein, vinyl ketones, acrylic acid derivatives, allylic and vinylic halides, as well as phosphorus and sulfur derivatives. Select examples of cross‐metathesis reactions involving the union of two complex substrates are then presented. Details provided include the relative stoichiometry of each coupling partner and catalyst loading, along with yields of by‐products and unreacted starting materials. Taken together, the examples within this chapter provide a wealth of information that can be used to design efficient cross‐metathesis based olefin functionalization or fragment coupling reactions.

Vinylic phenylsulfones containing a β-hydroxyl stereocenter undergo a diastereoselective isomerization to the corresponding allylic isomer upon treatment with 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU). Diastereoselectivity of this reaction increases with increasing size of the group attached to the carbinol carbon (up to >20:1 d.r. with a tert-butyl). Isolated yields of the isomerized allylic 1,2-hydroxy phenylsulfone products were comparable among the different vinylsulfones tested (59-66%). The major competing pathway was a C-C bond cleavage process, proposed to occur after the initial isomerization event. The sense of diastereoselection was consistent among all substrates investigated, in favor of the erythro-isomer based on NMR analysis.

Polyketides represent an important class of natural products with a broad range of interesting properties. This thesis describes the development of a new method for the preparation of anti-propionate subunits, a structural feature characteristic of polyketide natural products and the successful application of this method to the synthesis of dictyostatin-1, elaiolide, and halichoblelide aglycon. The idea that underpins the work described in this thesis is that a reductive cyclization of (silyloxy)enynes would provide a novel approach to the preparation of propionate subunits. A general method for the preparation and subsequent Ti(II)-mediated reductive cyclization of (silyloxy)enynes has been developed. The reaction scope and diastereoselectivity of the reaction has been demonstrated. The utility of this method in the context of complex polyketide natural product synthesis has been demonstrated by a total synthesis of dictyostatin-1, a member of an elite group of microtubule-stabilizing poyketides of marine origin that may serve as a lead for the development of new cancer therapeutics. Elaiolide and Halichoblelide represent structurally related polyketides. Embedded within their dimeric core is an anti-propionate subunit that was prepared by (silyloxy)enyne reductive cyclization. The resulting cyclic siloxane has been taken on to complete the synthesis of both natural products.