Total synthesis of solandelactones A, B, E, and F exploiting a tandem Petasis-Claisen lactonization strategy.
Solandelactones A, B, E, and F were synthesized using Nozaki-Hiyama-Kishi coupling of iododiene 13 with aldehydes 14 and 99 obtained by oxidation of alcohols 92 and 94. Key steps in the synthesis of 92 and 94 were (i) a Nagao asymmetric acetate aldol reaction of aldehyde 77 with thionothiazolidine 78 to set in place an alcohol that becomes the (7 S) lactone center of solandelactones, (ii) a Simmons-Smith cyclopropanation of 80 directed by this alcohol, and (iii) Petasis methylenation of cyclic carbonate 90 in tandem with a Claisen rearrangement that generates the octenalactone portion of solandelactones. Synthesis of solandelactones A, B, E, and F confirmed their gross structure and absolute configuration at C7, 8, 10, and 14 but showed that alcohol configuration at C11 must be reversed in pairs, A/B and E/F, from the previous assignment made to these hydroid metabolites. Thus, solandelactones A and B are correctly represented by 2 and 1, respectively, whereas solandelactones E and F are 6 and 5. A biogenesis of solandelactones is proposed for these C 22 oxylipins that parallels a hypothesis put forward previously to explain the origin of C 20 cyclopropane-containing algal products.
White
James D
JD
Department of Chemistry, Oregon State University, Corvallis, OR 97331-4003, USA. james.white@oregonstate.edu
Lincoln
Christopher M
CM
Yang
Jongtae
J
Martin
William H C
WH
Chan
David B
DB
D007783:Lactones / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D013055:Spectrophotometry, Infrared
D007783:Lactones