Myrcene. structure

Muscalure, structure of, 287 Mutarotation, 985-986 glucose and, 985-986 mechanism of. 986 Mycomycin, stereochemistry of, 330 Mylar, structure of, 819 n yo-Inositol, structure of, 135 Myrcene. structure of, 202 Mvristic acid, catabolism of, 1137 structure of. 1062... 

The structural feature that distinguishes terpenes from other natural products is the iso prene unit The carbon skeleton of myrcene (exclusive of its double bonds) corresponds to the head to tail union of two isoprene units... 

Propose a structure for myrcene, and write the reactions, showing starting material and products. 

K.J. van der Berg, J. ven der Horst, J.J. Boon, 0.0. Sudmeijer, Cis 1,4 poly P myrcene the structure of the polymeric fraction of mastic resin (Pistacia lentiscus) elucidated, Tetrahedron... 

The discussion of a series displacement index for classifying mass spectra and for correlation with structural stability includes some monoterpenoids e.g. myrcene limonene, santene). ... 

Monoterpenes are formed from two attached isoprene 3 units 2,6-dimethyloc-tane as the simplest skeleton. Thus, they can be acyclic or linear like -myrcene 4, ( )-/l-ocimene 5, (Z)-/l-ocimene 6, and allo-ocimene 7 (Structure 4.3). Or they can be cyclic, meaning ring-forming, such as in the simplest form like p-menthane 8 or p-cymene 9. Monocyclic 8, 9, bicyclic (5-3-carene 10 and tricyclic tricyclene 11 type monoterpenes are found in essential oils [1-4, 6-14, 16-23,38,39, 42, 47, 48]. 

These regular monoterpenes constitute a small class which includes the trienes myrcene 4 and ocimenes (5-7) and the alcohols geraniol 15, nerol 16, citronel-lol 17, linalool 18, etc (Structure 4.5). 

Camphorene 113 (Structure 4.34), which is a constituent of camphor oil, is identical to dimyrcene. Several dimyrcene derivatives are constituents of pistachio oils [54]. The gum resin of Commiphora mukul furnishes essential oil (0.4 %) consisting chiefly of myrcene 4 and dimyrcene (camphorene 113) [55]. 

Chemical structure-activity relationships suggested that phenolic monoter-penes (thymol, methyleugenol) seemed to be the most active, followed by alcohols (terpineol) and other oxigenated monoterpenes (1,8-cineole) [225, 229, 230]. Within the monoterpenes, -pinene was more active than a-pinene [226], and a-pinene was more active than caryophyllene and myrcene [234]. 

Terpenes are characterized as being made up of units of isoprene in a head-to-tail orientation. This isoprene concept, invented to aid in the structure determination of terpenes found in natural products, was especially useful for elucidation of structures of more complex sesquiterpenes, diterpenes, and polyterpenes. The hydrocarbon, myrcene, and the terpene alcohol, OC-terpineol, can be considered as being made up of two isoprene units in such a head-to-tail orientation (1). 

A wide variety of cyclic terpene hydrocarbons are known and, as multiples of CsH8, these have fewer double bonds than the open-chain terpenes. Because it is time consuming to show all the carbon and hydrogen atoms of such substances, the structures often are drawn in a convenient shorthand notation wherein the carbon-carbon bonds are represented by lines, carbon atoms being understood at the junctions or the ends of lines. By this notation, myrcene can be represented by formulas such as the following ... 

The common terpene names of a few acyclic hydrocarbons indicate the need for more precise names. For example, the name geraniolene, because of the "ol, suggests the presence of an OH group and some relation to the geraniols. From the name dihydromyrcene and a knowledge of the structure of myrcene, one cannot be sure where the two hydrogens have been added. The prefix alio- in allo-ocimene implies the more stable isomer, but knowledge of the structure of ocimene is insufficient to enable one to draw the correct formula for allo-ocimene. 

The common terpene names for acyclic terpene hydrocarbons are not sufficiently precise to indicate their structures or relationships among derivatives. It is recommended therefore that use of these names be discouraged, although the names allo-ocimene and myrcene will still be convenient for limited usage for commercial products. 

Figure 1.25 The isoprene rule for classifying compounds as terpenes. To apply the rule one ignores the double bonds (see myrcene) and in some cases it is also necessary to distort the isoprene structure (see a-pinene)...

The ozonolysis fragments from myrcene are 2-oxopentanedial (five carbon atoms), acetone (three carbon atoms), and two equivalents of formaldehyde (one carbon atom each). Putting these fragments together in a manner consistent with the data gives the following structural formula for myrcene ... 

Oximene and myrcene, two hydrocarbons isolated from alfalfa that have the molecular formula CioHie, both yield 2,6-dimethyloctane when treated with H2 and a Pd catalyst. Ozonolysis of oximene forms (CH3)2C=0, CH2=0, CH2(CHO)2, and CH3COCHO. Ozonolysis of myrcene yields (CH3)2C=0, CH2= O (two equiv), and HCOCH2CH2COCHO. Identify the structures of oximene and myrcene. 

Terpenes have a wide variety of structures. They can be acyclic or have one or more rings. They may have only carbon and hydrogen atoms, or they may have heteroatoms as well. The most common heteroatom in terpenes is oxygen. Many essential oils, a group of compounds isolated from plant sources by distillation, are terpenes. Examples include myrcene and menthol. 

In contrast, Rieke magnesium reacts with ( , )-1,4-diphenyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, isoprene, myrcene, or 2-phenyl-1,3-butadiene in tetrahydrofuran (THF) at ambient temperature to afford the corresponding substituted (2-butene-1,4-diyl)magnesium complexes in near quantitative yields. The structures of these complexes have not yet been determined except for (l,4-diphenyl-2-butene-l,4-diyl)magnesium, which has been shown to be a five-membered ring metallocycle [5]. Accordingly, the most likely structures for these complexes are five-membered metallocycles or oligomers. It is also possible that an equilibrium exists between these various forms. 

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