Total synthesis of (.+-.)-7-con-O-methylnogarol

Total Synthesis of (+)‐Rugulosin and (+)‐2,2′‐epi‐Cytoskyrin A through Cascade Reactions

“…Reasoning that the nature of the groups (R 1 ) residing on the C2/C2′ hydroxy groups may make a difference in the outcome of the anticipated reactions, we proceeded to construct different monomeric units as starting materials for the cascade. Scheme summarizes the synthesis of hydroquinones 11 a – 11 c featuring a Hauser annulation6 to construct the requisite tricyclic system. Thus, protection of the known diacetate 5 7 with MOMCl or TBSCl followed by desymmetrization using porcine liver esterase (PLE) at pH 8 afforded alcohols 6 a 8 or 6 b 7 in 95 and 90 % yield, respectively, over the two steps.…”

The Cytoskyrin Cascade: A Facile Entry into Cytoskyrin A, Deoxyrubroskyrin, Rugulin, Skyrin, and Flavoskyrin Model Systems

“…Scheme summarizes the synthesis of the first model system, bisanthraquinone 4 , through a sequence that features a Hauser annulation7 to construct the requisite tricyclic system and a radical dimerization to provide the required hexacyclic compound. Thus, treatment of nitrile 7 with LHMDS in THF at −78 °C, followed by addition of 2‐cyclohexenone (−78→25 °C) gave crude anthradihydroquinone 8 , which was directly subjected to methylation and dioxolane formation to afford protected compound 9 in 58 % overall yield for the three steps.…”

Studies toward the Total Synthesis of Nogalamycin: Construction of the Complete ABCDEF-Ring System via a Convergent Hauser Annulation

“…So far, the total synthesis of nogalamycin still remains to be an unaccomplished task, while the total synthesis of menogaril has been reported by both Terashima 14 and Hauser. 10 Terashima reported the first total synthesis of menogaril (Scheme 1), 14 in which a convergent annulation between naphthoquinone 3 and racemic diene 4 delivered the anthraquinone core structure 5, albeit in low yield. Unfavorable steric interactions within the proposed endo transition state resulted in a low yield of the desired product.…”

“…A few years later, Hauser's group reported a racemic total synthesis of menogaril (Scheme 1). 10 An efficient Hauser annulation between cyanophthalide 6 and α,β-unsaturated ketone 7 afforded the anthraquinone core structure 8. Multistep derivatization of the A-ring was then implemented to introduce the C-9 tertiary hydroxyl group, via a diastereoselective epoxidation/reduction sequence, with moderate selectivity.…”