ChemInform Abstract: Marrubinones A and B, New Labdane Diterpenoids from Marrubium astracanicum (Labiatae).

Abstract

Marrubinones A and B, New Labdane Diterpenoids from Marrubium astracanicum (Labiatae). -The two new diterpenoids (I) and (II) are isolated from the aerial parts of the title plants collected in Turkey. Their structures are characterized by modern NMR-techniques and some simple chemical transformations. The absolute configuration of (I) and (II) is determined by the modified Mosher method. -(IIDA, A.; TANAKA, Y.; MIHARA, T.; TABATA, M.; HONDA, G.; SHINGU, T.; TAKEDA, Y.; TAKAISHI, Y.; YESILADA, E.; SEZIK, E.; FUJITA, T.; Chem.

Total Syntheses of Marrubiin and Related Labdane Diterpene Lactones

“…While unprecedented in the transformation of the marrubiin class labdane diterpenoids, successive oxidations of a furan ring have been documented in semi-synthesis of the neoclerodane diterpene natural products salvinicins A and B by Prisinzano and co-workers [42]. Furthermore, Frontana-Uribe and co-workers reported construction of the [6,6,5,5]-tetracyclic framework, in which 4,5,6,7a-tetrahydro-2H-furo [2,3-b]pyran is spirolinked to a trans-decalin ring system, by an electrochemical oxidation of hispanolone [43]. When marrubiin (1) was exposed to pyridine tribromide in EtOH/CH 2 Cl 2 at 0 • C, oxidative acetalization occurred to give bisacetal 36 in 79% yield with a cis/trans ratio of 2:1, albeit with no sign of internal acetalization in contrast to Frontana-Uribe's work.…”

“…This furanoid natural product, formed from premarrubiin (2), was also reported to inhibit KCl-induced contraction of the rat aorta in a concentration-dependent manner [3]. The important pharmacological action of this family of mints prompted phytochemical analysis, leading to the isolation and characterization of a number of labdane diterpene lactones [4]: peregrinine (3) [5], marrubinones A (4) and B (polyodonine, 5) [6,7], velutines A (6), B (7) and C (8) [8], marrulibanoside (9) [9], marrulanic acid (10) [10], cyllenines A (11) and C (12) [11], marrulibacetal (13), marrulactone (14) [12], marrusidins A (15) and B (16) [13], marrulibacetal A (17), desertine (18) [14], and marrubasch F (19) [15] have been reported to date [16]. These natural products are biosynthesized from (E,E,E)-geranylgeranyl diphosphate (GGPP) through peregrinol diphosphate synthase (CPS1)-catalyzed bicyclization, followed by 9,13-epoxylabd-14-ene synthase (ELS)-catalyzed formation of tetrahydropyran and regiospecific oxygenations with P450s [17,18].…”