In 2012, a group led by Professor Masayuki Satake of the University of Tokyo reported the isolation and structure determination of a toxin from a marine algal bloom that decimated the fish population off the New Zealand coast in 1998. Extensive mass spectrometry and NMR experiments ultimately led to the structure shown below, named Brevisulcenal-F. (See Journal of the American Chemical Society, 2012, 134, 4963–4968.) This structure holds the record for the largest number of fused rings, at 17.

(a) How many ether groups are present?
(b) How many alcohol groups are present? Classify the alcohols as 1° or 2° or 3°.
(c) Are there any other oxygen-containing functional groups? Which, if any?

One of the crowning achievements of natural products synthesis was Bryostatin 1, published by Professor Gary Keck (University of Utah; Journal of the American Chemical Society, 2011, 133, 744–747). The Bryostatins are a family of compounds isolated from aquatic invertebrates known as Bryozoans. The compounds are of interest for a variety of biological effects, including anti-cancer activity and reversing brain damage in rodents.

(d) How many chiral centers are in this molecule?

(e) Using the number of chiral centers you reported in part (d), calculate the number of stereoisomers possible at these chiral centers. (Ignore stereoisomers at double bonds.)

A compound of molecular formula C₈H₈O gives the IR and NMR spectra shown here. Propose a structure, and show how it is consistent with the observed absorptions.

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Under the right conditions, the following acid-catalyzed double cyclization proceeds in remarkably good yields. Propose a mechanism. Does this reaction resemble a biological process you have seen?