In the Bosch synthesis of (1999, chiral) the olefin group in dione 1 was converted to an aldehyde by ozonolysis and chiral amine 2 was formed in a double reductive amination with (S)-1-phenethylamine. The phenylethyl substituent was removed using ClCOCHClCH and the enone group was introduced in a Grieco elimination using TMSI, HMDS then PhSeCl then ozone and then diisopropylamine forming carbamate 3. The amino group was deprotected by refluxing in methanol and then alkylated using (Z)-BrCHCICH=CHOTBDMS, to tertiary amine 4. A reductive Heck reaction took place next followed by methoxycarbonylation (LiHMDS, NCCOMe) to tricycle 5. Reaction with zinc dust in 10% sulfuric acid removed the TBDMS protective group, reduced the nitro group and brought about a reductive amino-carbonyl cyclization in a single step to tetracyclic 6 (epimeric mixture). In the final step to the Wieland-Gumlich aldehyde 7 reaction with NaH in MeOH afforded the correct epimer was followed by DIBAH reduction of the methyl ester.