Chapter 23, Problem 79CP

Two naturally occurring compounds that contain stable cyclic hemiacetals and acetals are monensin and digoxin, the chapter-opening molecule. Monensin, a polyether antibiotic produced by Streptomyces cinamonensis, is used as an additive in cattle feed. Digoxin is a widely prescribed cardiac drug used to increase the force of heart contractions. Label each acetal, hemiacetal, and ether in both compounds.

A key step in the synthesis of β-vetivone, a major constituent of vetiver, a perennial grass found in tropical and subtropical regions of the world, involved the reaction of compound A and dihalide B with two equivalents of LDA to form C. Draw a stepwise mechanism for this reaction. β-Vetivone contains a spiro ring system—that is, two rings that share a single carbon atom.

Label the alkene in each drug as E or Z. Enclomiphene is one component of the fertility drug Clomid. Tamoxifen is an anticancer drug. Clavulanic acid is sold in combination with the antibiotic amoxicillin under the trade name Augmentin.