Croton species

Ferreira, D. et al.. Circular dichroic properties of flavan-3,4-diols, J. Nat. Prod., 67, 174, 2004. Cai, Y. et al.. Biological and chemical investigation of dragon s blood from croton species of South America. Part 1. Polyphenolic compounds from Croton lechleri. Phytochemistry, 30, 2033, 1991. Cui, C.B., Davallin, a new tetrameric proanthocyanidin from the rhizomes of Davallia mariesii Moore, Chem. Pharm. Bull, 39, 2179, 1991. 

The earliest isolation of this base from the Croton species (pcs 261 64) was a mixture of alkaloids that was given the name Homolinearisine. Subsequent purification showed it to be N-Methylcrotonosine (jcs 1676 66). 

Ricin was found by Stillmark in 1889 as the first plant lectin derived from the seeds of the castor plant, Ricinus communis L., a member of the Euphorbiaceae or spurge family. Other members of this family include the popular houseplants poinsettia E. pulcherrima), and the croton species. The term castor bean is used commonly to refer to both the plant and seed of R. communis. Ricinus communis commonly grows along streams and riverbeds in addition to subtropical locations high in nutrients. Ricinus communis is a coarse perennial, 10-13 m tall in the tropics, with a stem 7.5-15 cm... 

Although the absolute configuration of these clerodanes from Croton species was not determined, the absolute stereochemistry of a number of clerodanes from Teucrium (Labiatae) species has been clarified.39 19-Acetylgnaphalin and iso-fruticolone were shown to belong to the neoclerodane series. Teuflin (24) has been obtained40 from Teucrium viscidum and details of an X-ray structure have been published.41 The structure (25), without absolute configuration, was assigned42 to... 

A further pair of alcohols, (1) and (2), derived from geranylgeraniol and showing inhibitory action against ulcers, has been obtained from Croton species. Similar compounds [e.g. (3) and (4)] and some prenylated monoterpenoid skeleta such... 

Salatino A, Salatino MLF, Negri G (2007) Traditional uses, chemistry and pharmacology of Croton species (Euphorbiaceae). J Braz Chem Soc 18(l) ll-33. doi 10.1590/s0103-50532007000100002... 

Such deprotonation/elimination side reactions yield either acrylate (from P-propiolactone) or crotonate species (P-butyrolactone) that are also capable of... 

Examples of prolate near-symmetric rotors are the s-trans and s-cis isomers of crotonic acid, shown in Figure 5.8, the a axis straddling a chain of the heavier atoms in both species. The rotational term values for both isomers are given approximately by Equation (5.37) but, because A and B are different for each of them, their rotational transitions are not quite coincident. Figure 5.9 shows a part of a low-resolution microwave spectmm of crotonic acid in which the weaker series of lines is due to the less abundant s-cis isomer and the stronger series is due to the more abundant s-trans isomer. 

A number of activated olefinic compounds react very weU in this scheme including methacrylates, crotonates, acrylonitrile, and vinyl ketones. These reactions are typicaHy mn in an etherial solvent and can be mn without the complications of undesirable side reactions leading to trialkylated tin species. 

When the epoxy-isobutenyl ester of crotonic acid is treated with the Cp2ZrCl2/AgC104 Lewis acid, the epoxide is opened by intramolecular assistance of the ester carbonyl group, giving a dioxolenium cation (Scheme 8.49). This species is a highly electrophilic Diels—Alder dienophile that reacts with a range of dienes. THF deactivates cationic zirconocene species and is therefore not tolerated as a solvent [89]. 

The species with the higher allelopathic potentials were Piper auritum. Piper hispidum, Croton pyramidalis, and Siparuna nicaraguen-sis. The essential oils of the Piperaceae were highly inhibitory while that of Croton pyramidalis was less inhibitory and even produced stimulations (Table III). 

Table I. Effects of the Extracts of Leaves and Roots of Piper aurltum, . hlspldum, Croton pyramldalis, Cecropla obtuslfolla, and Slparuna nlcaraguensls on Radicle Growth of Some Secondary Species...

A second-order dependence on crotonic acid has been observed in its Os(VIII)-catalysed oxidation with CAT in alkaline solution. The reaction rate varied linearly with the concentration of Os(VIII). A mechanism has been proposed.140 The kinetics of the ruthenium(III)-catalysed oxidation of the secondary amines with CAT in acidic medium have been obtained and mechanisms have been postulated.141 Uncatalysed and Ru(III)-catalysed oxidation of ethylenediamine, diethylenetriamine, triethylenete-tramine, aminoethylpiperazine, and isophoronediamine with CAT in HC1 solution showed a fractional dependence on the amine, hydrogen ions, and Ru(III), and it is independent of CAT concentration. TSNH2CI has been postulated as the reactive species and a mechanism has been suggested.142... 

Table 10.1 presents typical specifications for a polymerization-grade product, as well as some physical properties. Prohibited impurities refer to inhibitors (croton-aldehyde, vinyl acetylene), chain-transfer agents (acetic acid, acetaldehyde, acetone) and polymerizable species (vinyl crotonate), while methyl and ethyl acetate impurities are tolerated. 

The reduction potential of l-chloro-3-methyl-2-butene (41) is more positive than that of methyl crotonate which results in the initial 2-electron reduction of the allyl halide to give the allyl ion. This species subsequently undergoes Michael reaction through the tertiary... 

It seems obvious that the same mechanism could also apply to the cyclopropanation of the fran,s-crotonic ester (Figure 9.3, bottom). A Michael addition of the S ylide would then convert it directly into the ester enolate B. This species would cyclize exclusively to the fratw-disubstituted cyclopropane exactly as when it is produced from the cis-crotonic ester in two steps via the conformer A. 

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