A blueprint for controlling the stereochemistry of oxygenated 5,5-spiroketals using chelation effects is provided. Chelation specifically of zinc salts (other protic and Lewis acids were less effective) between the spiroketal oxygen and an appropriately positioned alcohol group overrides normal biases in the preparation of 5,5-spiroketals, as illustrated by the stereocontrolled synthesis of epimeric cephalosporolide H isomers. This study provides new and valuable information for prescribing the chirality of the stereogenic core of 5,5-spiroketals.

The first synthesis of a strained six-membered cyclic ynamide is described. N-Tosyl-3-azacyclohexyne is generated via fluoride-promoted 1,2 elimination under conditions that allow trapping of the strained heterocyclic alkyne in a variety of addition, insertion, and [2 + 2], [3 + 2], and [4 + 2] cycloaddition reactions.

COVID-19 caught everyone by surprise, and the situation quickly escalated from epidemic to pandemic. By February 21, 2020, the first positive case was reported in Lebanon, and following that, by March 12, 2020, the decision to close all educational institutes was put into effect. Online learning is not an approved form of education in Lebanon, which meant that none of the Lebanese universities was prepared to make a complete shift from face-to-face learning to online learning. Immediate actions were taken at the Lebanese International University starting at the level of the University Council, all the way to the level of individual departments. The approach of the Department of Biological and Chemical Sciences is best described as “break barriers, build bridges, and launch transitions”. An initial assessment of strengths and weaknesses helped the department develop a model of online learning that took advantage of the readily available online tools (e.g., Google Classroom) while modifying the format of content delivery and assessment with the minimal potential for disruption by inadequate Internet, interruptions in electricity, and limited access to expensive hardware and software. A SWOT analysis of the model was done based on the survey that was given to the chemistry instructors in the department while taking into consideration the emails and comments received by students.

SummaryThe synthesis of four candidate stereoisomers of cephalosporolide H is described, made possible by a zinc-chelation strategy for controlling the stereochemistry of oxygenated 5,5-spiroketals. The same strategy likewise enables the first stereocontrolled synthesis of cephalosporolide E, which is typically isolated and prepared admixed with its spiroketal epimer, cephalosporolide F.

SummaryA highly efficient synthesis of oxygenated 5,5-spiroketals was performed towards the synthesis of the cephalosporolides. Gold(I) chloride in methanol induced the cycloisomerization of a protected alkyne triol with concomitant deprotection to give a strategically hydroxylated 5,5-spiroketal, despite the potential for regiochemical complications and elimination to furan. Other late transition metal Lewis acids were less effective. The use of methanol as solvent helped suppress the formation of the undesired furan by-product. This study provides yet another example of the advantages of gold catalysis in the activation of alkyne π-systems.