Lactones in the Synthesis of Prostaglandins and Prostaglandin Analogs

In the total stereo-controlled synthesis of natural prostaglandins (PGs) and their structural analogs, a vast class of compounds and drugs, known as the lactones, are encountered in a few key steps to build the final molecule, as: δ-lactones, γ-lactones, and 1,9-, 1,11-, and 1,15-macrolactones. After the synthesis of 1,9-PGF2α and 1,15-PGF2α lactones, many 1,15-lactones of E2, E3, F2, F3, A2, and A3 were found in the marine mollusc Tethys fimbria and the quest for understanding their biological role stimulated the research on their synthesis. Then 1,9-, 1,11-, and 1,15-PG lactones of the drugs were synthesized as an alternative to the corresponding esters, and the first part of the paper describes the methods used for their synthesis. The efficient Corey procedure for the synthesis of prostaglandins uses the key δ-lactone and γ-lactone intermediates with three or four stereocenters on the cyclopentane fragment to link the PG side chains. The paper describes the most used procedures for the synthesis of the milestone δ-Corey-lactones and γ-Corey-lactones, their improvements, and some new promising methods, such as interesting, new stereo-controlled and catalyzed enantioselective reactions, and methods based on the chemical/enzymatic resolution of the compounds in different steps of the sequences. The many uses of δ-lactones not only for the synthesis of γ-lactones, but also for obtaining 9β-halogen-PGs and halogen-substituted cyclopentane intermediates, as synthons for new 9β-PG analogs and future applications, are also discussed.

Fossil molluscs from borehole Hollum (Ameland, the Netherlands) constrain three successive Quaternary interglacial marine intervals in the southern North Sea Basin

When dealing with stratigraphic successions in marginal basin settings, the geological record is often fragmented due to erosion and reworking processes. The North Sea Basin is an example: it has a fragmented Quaternary record; in particular, Middle Pleistocene intervals are poorly known. As a result, we have little insight into climate, marine environmental conditions and biodiversity in this period. Here we describe and discuss a succession of three interglacial marine mollusc-bearing intervals in a borehole from Ameland in the northern Netherlands (borehole B01H0189 near Hollum). These intervals are attributed to marine isotope stages MIS7, MIS5e and MIS1. The Holocene Celtic type of faunas (interval 0–26.24 m below surface (b.s.)) and Eemian Lusitanian type of faunas (26.24–30.40 m b.s.) are well-known from previous research. The newly reported MIS7 Oostermeer fauna (32.80–39.00 m b.s.) represents mostly full marine settings between storm wave base and fair-weather wave base. In composition and diversity, the MIS7 and MIS1 faunas strongly resemble and differ from the MIS5e fauna. This is the first well-documented record of three stacked marine interglacial assemblages from the southern North Sea Basin at one location. This new record enables us to make complete marine faunal characterisations of successive interglacial periods. Key implications for southern North Sea stratigraphy and palaeogeography are the resemblance of marine faunas and conditions in MIS7 and MIS1, the presence of a relatively warm latest MIS6 freshwater interval and confirmation and characterisation of the warm Eemian interval north of the classical type area.

Large-scale project ‘Chiton of the Mexican Tropical Pacific’: Chiton articulatus (Mollusca: Polyplacophora)

The marine mollusc, commonly called sea cockroach or chiton Chiton articulatus, is a mollusc belonging to the group known as Polyplacophora because its shell is composed of eight individual plates. This mollusc inhabits the rocky intertidal shore of the Mexican Tropical Pacific, where it is endemic. It has ecological, but also economic, importance. Ecologically, it is the preferred food of the snail Plicopurpura pansa, a protected species, in the cultural heritage of the country. Additionally, it is a basibiont (generates substrate for other individuals) that maintains the biodiversity of the Region. Economically, it has changed from artisanal consumption to become a culinary tourist attraction, offered at restaurants as an exotic and aphrodisiac dish, in tourist places like Huatulco or Acapulco. Despite being an exploited resource for decades, little is known about its life history. The Mexican Authorities have not yet recognised this mollusc as a fishing resource, so that it does not have any law that controls its extraction, sale and consumption, putting at risk the recruitment, survival and permanence of this species. The goal of this project is the preservation and support for the management of the species. The Project "Quiton del Pacifico Tropical Mexicano" seeks to provide the biological, ecological, reproductive, genetic, anatomical and morphometric bases of the populations of Chiton articulatus. The project was structured in four stages: 1) field sampling and obtaining samples, 2) disclosure and presentation of the project, 3) inclusion of students at the undergraduate and graduate level, 4) application of results. The inclusion and recognition of C. articulatus as a fishing resource will achieve impact at the national and regional level through the implementation of laws that regulate its fishing, as well as its inclusion in management and food security policies. Additionally, this Mexican Chiton Project is currently replicating with chiton species in Galapagos, Ecuador.

Evolved differences in energy metabolism and growth dictate the impacts of ocean acidification on abalone aquaculture

Ocean acidification (OA) poses a major threat to marine ecosystems and shellfish aquaculture. A promising mitigation strategy is the identification and breeding of shellfish varieties exhibiting resilience to acidification stress. We experimentally compared the effects of OA on two populations of red abalone (Haliotis rufescens), a marine mollusc important to fisheries and global aquaculture. Results from our experiments simulating captive aquaculture conditions demonstrated that abalone sourced from a strong upwelling region were tolerant of ongoing OA, whereas a captive-raised population sourced from a region of weaker upwelling exhibited significant mortality and vulnerability to OA. This difference was linked to population-specific variation in the maternal provisioning of lipids to offspring, with a positive correlation between lipid concentrations and survival under OA. This relationship also persisted in experiments on second-generation animals, and larval lipid consumption rates varied among paternal crosses, which is consistent with the presence of genetic variation for physiological traits relevant for OA survival. Across experimental trials, growth rates differed among family lineages, and the highest mortality under OA occurred in the fastest growing crosses. Identifying traits that convey resilience to OA is critical to the continued success of abalone and other shellfish production, and these mitigation efforts should be incorporated into breeding programs for commercial and restoration aquaculture.

Animal size and seawater temperature, but not pH, influence a repeatable startle response behaviour in a wide-ranging marine mollusc

Startle response behaviours are important in predator avoidance and escape for a wide array of animals. For many marine invertebrates, however, startle response behaviours are understudied, and the effects of global change stressors on these responses are unknown. We exposed two size classes of blue mussels (Mytilus edulis × trossulus) to different combinations of temperature (15 and 19 °C) and pH (8.2 and 7.5 pHT) for three months and subsequently measured individual time to open following a tactile predator cue (i.e., startle response time) over a series of four consecutive trials. Time to open was highly repeatable on the short-term and decreased linearly across the four trials. Individuals from the larger size class had a shorter time to open than their smaller-sized counterparts. High temperature increased time to open compared to low temperature, while pH had no effect. These results suggest that bivalve time to open is repeatable, related to relative vulnerability to predation, and affected by temperature. Given that increased closure times impact feeding and respiration, the effect of temperature on closure duration may play a role in the sensitivity to ocean warming in this species and contribute to ecosystem-level effects.