On the proposed structures and stereocontrolled synthesis of the cephalosporolides

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2012, 8, 1287–1292, doi:10.3762/bjoc.8.146

• 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. Keywords: cephalosporolides; chelation

• cephalosporolide E for the first time in a stereocontrolled manner. Pheromone spiroketals. Reported structures of the cephalosporolides and penisporolides. Reported and synthesized cephalosporolide H isomers. Stereocontrol of oxygenated 5,5-spiroketals. Synthesis of the reported cephalosporolide H and its spiro

• silyl ether 19 with the (R)-propylene oxide produced the internal alkyne 20 (Scheme 5). Gold(I) chloride in MeOH induced the spiroketalization of alkyne 20 with concomitant cleavage of the PMP acetal and partial cleavage of the TBS ether. After completion of the desilylation with TBAF, a mixture of 5,5

A gold-catalyzed alkyne-diol cycloisomerization for the synthesis of oxygenated 5,5-spiroketals

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2011, 7, 570–577, doi:10.3762/bjoc.7.66

• Sami F. Tlais Gregory B. Dudley Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390 USA, Fax: (850) 644-8281 10.3762/bjoc.7.66 Abstract A highly efficient synthesis of oxygenated 5,5-spiroketals was performed towards the synthesis of the

• ; 5,5-spiroketals; Introduction Spiroketals, exemplified by structure shown in Figure 1, are prominent structural features of many biomedically relevant natural and non-natural target structures [1][2][3][4]. As such, the synthesis of spiroketals has received considerable attention, with most progress

• having been made on systems that include at least one six-membered ring [5]. 5,5-Spiroketals (m, n = 0, Figure 1), particularly oxygenated 5,5-spiroketals such as are found in the cephalosporolides (Figure 2), are the focus of this study. A variety of synthetic methods are available for the synthesis of