Reactivity of Chiral Sesquiterpene Synthons Obtained by the Degradation of Maslinic Acid from Olive‐Pressing Residues.

Abstract

Terpenes U 0200Reactivity of Chiral Sesquiterpene Synthons Obtained by the Degradation of Maslinic Acid from Olive-Pressing Residues. -The chemical behavior of cis-and trans-decalin chiral synthons derived from oxidative fragmentation of maslinic acid, i.e. (I), (IX) and (XI), is studied in detail. These synthons permit access to phenanthrene-and drimane-type compounds and to natural tricyclic triterpenes. -(GARCIA-GRANADOS, A.; LOPEZ, P. E.; MELGUIZO, E.; PARRA*, A.; SIMEO, Y.; Synth.

Advances in the Semi-Synthesis of Triterpenoids

“…Reductive elimination of the acetoxy lactone moiety of 47 occurred efficiently via lithiumliquid ammonia reduction to provide the myricerone ethylene ketal intermediate quantitatively, which was then subjected to deketalization under acidic conditions to deliver myricerone 48 (89%, 2 steps). The introduction of a caffeoyl group to C27-OH of 48 was achieved by a stepwise procedure comprising esterification with diethoxyphosphonoacetic acid and Horner-Wadsworth-Emmons (HWE) olefination with 3,4-bis(benzyloxy)benzaldehyde (49). The resulting caffeoylated intermediate was then subjected to acid-mediated debenzylation to give the target molecule myriceric acid A (50) (64%, 3 steps).…”

“…Baldwin's oxime method has found exquisite applications in the synthesis of hederagenin and hyptatic acid A with the C23 and C24 methyl groups of the oleanane derivatives functionalized, respectively (Scheme 9). 32 Commencing with methyl oleanate (18), 3-oxime 51 was obtained by successive oxidation and condensation with hydroxylamine (88%, 2 steps). The obtained oxime was palladated with Na 2 PdCl 4 to give a dimeric organopalladium complex intermediate (90%).…”

“…Furthermore, upon irradiation of homodiene 109, the C-ring ruptured triterpenoid triene 110 was rendered in 96% yield, which was generated through a conrotatory photochemical electrocyclic mechanism. 47 seco-Triterpenoids provide opportunities to access derivatives with deeper modified chemical space, thus potentially leading to the discovery of compounds with improved medicinal features. As a pertinent example, the synthesis of epiceanothic acid (117), a triterpenoid derivative with a contracted as well as cis-arranged OH-and COOH-decorated A ring, was accomplished with a seco-diacid as the key intermediate (Scheme 20).…”

“…When isolated 119 was re-irradiated under the same conditions for an extra 30 minutes, a photocatalyzed [2+2]-cyclization took place to provide cyclobutane 120 (50%), which was extremely difficult to access when easily available triterpenoids were selected as feedstocks (Scheme 21). 49…”

A Partial Synthesis of 23-Hydroxybetulonic Acid and 23-Hydroxybetulinic Acid Starting from Betulinic Acid

“…18,19 This method has been extensively used in the synthesis of natural triterpene compounds. 20,21 These results led us to propose the key step by cyclopalladation of the 23-methyl group from a 3-one oxime functionality of 1 to obtain 2 and 3. We now report a semisynthetic approach to 2 and 3 starting from 1 by using this method.…”