Of diterpenoids

Sultankhodzhaev MN et al. (2005) Tyrosinase inhibition studies of diterpenoid alkaloids and their derivatives structure-activity relationships. Nat Prod Res 19(5) 517-522... 

Slamenova D, Masterova I, Labaj J, et al. Cytotoxic and DNA-damaging effects of diterpenoid quinones from the roots of Salvia officinalis L. on colonic and hepatic human cells cultured in vitro. Basic Clin Pharmacol Toxicol 2004 94 282-290. 

In 2011, Hartwig and coworkers reported the total synthesis of taiwaniaquinol B (55, Scheme 11.9), a member of a family of diterpenoids that are derived from the abietane skeleton [36]. A key aspect of the Hartwig synthesis of taiwaniaquinol B was the use of the iridium-catalyzed borylation reaction to accomplish the C(5) functionalization of resorcinol derivative 53. This regioselectivity for the overall bromination is complementary to that which would be obtained using a standard electrophilic aromatic substitution (EAS) reaction. In the transformation of 53 to 54, a sterically controlled borylation was first accomplished, which was then followed by treatment of the boronic ester intermediate with cupric bromide to... 

Resins older than 40 000 years are considered to be fossil resins. The fossilization of resins begins with polymerisation and forms ambers and copals. Most of the ambers are derived from components of diterpenoid resins with a labdanoid structure other ambers are based on polymers of sesquiterpene hydrocarbons such as cadinene, and may include triterpenoids less common ambers from phenolic resins derive from polymers of styrene. Figure 1.4 shows the skeletal structures of the components which make up the polymers occurring in fossil resins [141]. 

Figure 5.10 GALDI mass spectrum of rosin (colophony from THF solution). The typical signal pattern of diterpenoids is visible m/z 325 corresponds to isomeric diterpenoid acids, e.g.

Table 5.3 Prominent peaks in the mass spectrum of rosin (see Figure 5.10). Compounds marked with an asterisk are mentioned as constituents of diterpenoid varnishes from old pictures in the literature...

Py-GC/MS characterisation of diterpenoid resins using online trimethilsilylation with HMDS has been performed on fresh Pinaceae resins, manila Copal, sandarac, and Copaiba... 

L. Osete Cortina and M.T. Domenech Carbo, Analytical characterization of diterpenoid resins present in pictorial varnishes using pyrolysis gas chromatography mass spectrometry with on line trimethylsilylation, J. Chromatogr., A, 1065, 265 278 (2005). 

More recently on-line pyrolysis with HMDS has been performed successfully even if the pyrolysis interface was kept at 250°C. In fact, Domenech-Carbo and colleagues [57,58] have obtained very good results on a variety of art materials and on real paint samples as well. They have applied Py-GC/MS with on-line trimethylsilylation to the characterization of diterpenoid resins and, in contrast to previous literature data, the derivatization method enabled not only the identification of resinous carboxylic acids in the form of TMS esters, but also an efficient conversion of hydroxyl groups to TMS ethers. 

Although HMDS seems to promote dehydration more than TMAH, the number of side reactions occurring upon methylation of diterpenoids is reduced by using trimethylsilylation and as a consequence more simplified chromatograms are obtained. This is in addition to a general improvement in sensitivity and better resolution of some representative peaks. 

Anionic oxy-Cope rearrangement was also employed for the enantioselective total synthesis of compounds related to marine metabolites (equation 230)305 307, as well as for the preparation of diterpenoide vinigrol (equation 231)308 and cerorubenic acid-in... 

Okada A, Okada K, Miyamoto K, Koga J, Shibuya N, Nojiri H, Yamane H (2009) OsTGAPl, a bZlP transcription factor, coordinately regulates the inductive production of diterpenoid phytoalexins in rice. J Biol Chem 284 26510-26518... 

Fig. 1. Scheme for the alteration of diterpenoid natural product precursors to saturated and aromatic derivatives (natural product examples are boxed, stereochemistry is indicated where known). 

This chapter follows the pattern of the previous Reports, with sections based on the major skeletal types of diterpenoid. The literature which has been covered is that available to August 1977. 

Grayanotoxins.—Pieris japonica (Ericaceae) contains a number of diterpenoid toxins. An X-ray analysis of pieristoxin G (100) has been published and the structures (101)—(103) have been assigned to asebotoxins VI, VIII, and IX respectively. 

Fast-atom bombardment mass spectrometry (FAB-MS) has been applied to the identification of diterpenoid compounds and their oxidation products. Similarly, laser-induced desorption mass spectrometric (LDMS) techniques have been applied to the identification of natural and synthetic organic pigments in microscopic paint samples prepared as cross sections [60]. 

A very large number of diterpenoids possessing a labdane skeleton (1), Fig. (7), occur in nature [34]. The interest in studing labdanes is... 

The conifers are an important source of diterpenoids. Several labdanes have been detected in the neutral fraction of the oleoresin of Araucaria excelsa, including manool as well as nor-labdanes [42]. Some neutral diterpenoids, such as enMabd-8, 13(E)-dien-15-ol and its acetate, were obtained after extraction of the resin of Araucaria bidwillii [43], while the normal series of the above labdanes have been isolated from Cistus creticus subsp. creticus [44]. From Pinus sylvestris, 3P-hydroxybiformene has been obtained, while from the needles of the American red wood pine (Pinus resinosa), 8,13-epoxy-labd-14-en-19-oic acid, was isolated. In Pinus nigra, labdane acids have been found to be the major acid components of its needles [45,46]. The occurrence of diterpenoids including labdanes in conifers has been published as a review of the chemistry of the order Pinales [47],... 

The most important manoyl oxide derivative is forskolin (9), Fig. (7), (7p-acetoxy-8, 13-epoxy-la, 6p, 9a-trihydroxylabd-14-en-ll-one) [151-153]. It belongs to the labdane series of diterpenes and was isolated from the Indian herb Coleus forskohlii (Willd.) Briq. (Labiatae). Since ancient times it has been used in Hindu and Ayurvedic traditional medicine [154]. The plant Coleus forskohlii (Willd.) Briq. has been extensively studied, and from its extracted roots a group of diterpenoids, with the basic skeleton of 11-oxo-manoyl oxide, have been isolated. The main compound, forskolin, presented remarkable chemical and biological properties [155]. Analogues of forskolin were then prepared by semisynthesis [156] or obtained by microbial transformations [157]. New analogues, more soluble than forskolin have shown activities comparable to and even higher than forskolin [158]. 

Carbon-13 and Proton NMR Shift Assignments and Physical Constants of Diterpenoid Alkaloids... 

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