Synthesis of 5,6- and 6,6-Spirocyclic Compounds

Recent developments in transition metal-catalysed spiroketalisation

“…These include transition metal-catalysed spiroketalisation of alkynes and alkenes, hetero-Diels-Alder reactions, and oxidative radical cyclisations. 4,5 The utilisation of transition metals for the synthesis of spiroketals has attracted significant attention. In particular, Pd II , Pt II , Au I , Au III , and Re VII have all been investigated for their ability to construct the spiroketal moiety.…”

A Route to 5,5-Dithiospiroketals and to Long-Chain Monomers from the Biomass

“…In contrast to the ubiquitous spiroketals, which are found in plants, insects, marine organisms, microbes, and fungi (three examples, 1 – 3 , are displayed in Figure ), dithiospiroketals, their sulfur counterparts, are almost unknown. No such compounds have so far been found in nature, and only two synthetic derivatives have been reported, the parent 1,6-dithiospiro­[4,4]­decane 6 and its dibenzo analogue 8 , as well as their corresponding bis-sulfones 7 and 9 (Scheme ).…”

Gene Cluster Activation in a Bacterial Symbiont Leads to Halogenated Angucyclic Maduralactomycins and Spirocyclic Actinospirols

“…Whereas maduralactomycins ( 1 , 2 ) partially resemble kinamycin-type compounds, such as dehydrorabelomycin, kinobscurinone, and stealthin C, actinospirols ( 3 , 4 ) feature a highly intriguing five-membered spiroketal moiety similar to the core moiety of rubromycin polyketides and the antibacterial natural product armeniaspirols derived from Streptomyces and pseurotin A from Aspergillus. , Because both compounds 1 and 3 share similar structural elements, we hypothesized that both share the same biosynthetic origin but might have undergone different levels of oxidative post-polyketide synthase (PKS) modifications such as C–H bond oxidation or Baeyer–Villiger-type oxidative rearrangements.…”