Synthesis of substances related to Gibberellins—XXIV

Synthesis of Functionalized Bicyclo[3.2.1]octanes and Their Multiple Uses in Organic Chemistry

“…The pioneering work of Loewenthal's group directed toward the synthesis of compounds related to gibberellic acid showed the feasibility of such an electrophilic acylation in the case of keto acid 103 which was easily transformed, upon reaction with BF 3 ·OEt 2 , to the tetracyclic ketone 104 , a precursor of gibberone. Adaptation of this strategy was proposed subsequently for the synthesis of d -phyllocladene and Garrya veatchii alkaloids …”

“…Closely related to these carbocationic rearrangements is the intramolecular pinacol condensation of bicyclo[2.2.2]octanediones of type 517 , giving hydroxy bridgehead bicyclic octanones 518 which was applied to the total syntheses of steriol and epiallogibberic acid …”

Total Synthesis of Four Classes of Daphniphyllum Alkaloids

“…On the one hand, the biogenesis of 9 from daphniyunnine A ( 7 ) ( 7 → 9 , Figure A) involves formal oxygen atom insertion into the C10–C17 bond, which is difficult for us to imitate directly. On the other hand, the biogenetic pathway from 9 to daphnicyclidin D ( 11 ) ( 9 → 11 , Figure A) features an intriguing process of C1–C8 bond cleavage and C1–C13 bond formation, presumably with the intermediacy of a cyclopropanol species (such as 37 ), which originates in an insightful cyclization–fragmentation hypothesis proposed by Yue and co-workers. ,− However, a suitable reaction mode on the basis of this hypothesis has yet to be established in practice. Therefore, we designed compound 9′ (Figure B) as a common intermediate for the synthesis of the daphnilongeranin A-type and daphnicyclidin D-type alkaloids.…”

Synthesis of Phytohormones, Phytoalexins and Other Biofunctional Molecules of Plant Origin

“…The amounts of homodolicholide (32) 75 and homodolichosterone (35) 76 isolated from Dolichos lablab were only 12 μg and 20 μg, respectively. It was therefore necessary to synthesize them in substantial amounts so as to evaluate their plant-growth-promoting activity.…”