A-Carbon skeleton

The shorter form implies no additional carbon atoms, and is used when the group is part of a chain. The long form implies one more carbon atom than the parent stmcture, and is used when the group is attached to a ring, or for other reasons is not conveniently named as part of a carbon skeleton. 

Amino group An -NH2 group attached to a carbon skeleton as in the amines and amino acids. 

This next example involves the well-known plant kawa. A psychoactive beverage made from the roots of this plant is used widely in the islands of the southwestern Pacific Ocean either for ritualistic or routine consumption. Kava is the common name for Piper methysticum Forst. f. from which several compounds responsible for the pharmacological activity have been isolated and identified. Representative structures of the family of styrylpyrones, commonly called kavalactones, are given in Fig. 6.6. The compounds are based upon a carbon skeleton consisting of a styryl function (C C ) attached to a six-membered lactone ring. The fundamental compound, kawain, is shown as structure [547]. Structural variants include... 

Identification of 9,12-tetradecadienyl (9,12-14) compounds began with studies on two cosmopolitan pests of stored products, the almond moth (Cadra cmtella, Pyralidae Phycitinae) and the Indian meal moth (Plodia interpunctella, Phycitinae) [38,39]. This 9,12-14 structure has been reported from another 13 Pyralidae (only in Phycitinae) species and 11 Noctuidae species (9 species in Amphipyrinae, and 1 species each in Hadeninae and Plusiinae). These two families, however, are not closely related. Most likely, the females classified in distant groups happened to produce the same chemical in the train of their perpetual evolution of modifying the original systems for pheromone biosynthesis. The 5,7-dodecadienyl (5,7-12) structure is a carbon skeleton common... 

Figure 4.12 Representations of the chair conformation of cyclohexane (a) Carbon skeleton only (b) Carbon and hydrogen atoms (c) Line drawing (d) Space-filling model of cyclohexane. Notice that there are two types of hydrogen substituents—those that project obviously up or down (shown in red) and those that lie around the perimeter of the ring in more subtle up or down orientations (shown in black or gray). We shall discuss this further in Section 4.13.

Figure 4.16 (a) Carbon skeleton and (b) line drawing of the twist conformation of cyclohexane. 

A given organic molecule is generally composed of a carbon skeleton and functional groups. A name matches a structure when the name of the parent hydride corresponds to the skeleton, while prefixes and sufiixes represent the functional groups and other structural characteristics, such as geometry. 

The high synthetic utility of alcohols 38 stems from the fact that terminal alkynes are among the most versatile functional groups for the further elaboration of a carbon skeleton. Asymmetric synthesis of alcohols 38 from aldehydes with the concurrent formation of the two stereogenic C atoms has been accomplished mainly by two methods. The first features synthesis of chiral nonracemic allenylmetal compounds from the corresponding chiral nonracemic propargyl alcohols and addition of the former to aldehydes [26] and the second method in-... 

The desulfurative C-C bond formation process developed by Eschenmoser [217] is somewhat akin to the Ramberg-Backlund rearrangement. An episulfide intermediate is formed, which on being attacked by a phosphine, begets a carbon skeleton with polarity alternating sequence. 

Chalcones are unsaturated and, along with dihydrochalcones, contain an open pyronic cycle and a carbon skeleton numbered in a way different from other flavonoids, Fig. (8, 9). Native chalcone glycosides tend to transform into flavanone glycosides during extraction procedures. Chalcones per se are therefore of restricted occurence in foods [35]. 

Let us start out by a few comments about the terms used to describe carbon skeletons encountered in organic molecules. When considering a hydrocarbon (i.e., a compound consisting of only C and H) or a hydrocarbon group (i.e., a hydrocarbon substituent) in a molecule, the only possible functionalities are carbon-carbon double and triple bonds. A carbon skeleton is said to be saturated if it has no double or triple bond, and unsaturated if there is at least one such bond present. Hence, in a hydrocarbon, the term saturated indicates that the carbon skeleton contains the maximum number of hydrogen atoms compatible with the requirement that carbon always forms four bonds and hydrogen one. A saturated carbon atom is one that is singly bound to four other separate atoms. 

Not only are the carbon skeletons of these substances divisible into isoprene units, but the terpene hydrocarbons are usually exact multiples of C5H8. An example is myrcene (Cl0H16), which occurs in the oils of bay and verbena and has a carbon skeleton divisible into two isoprene units. (Also see Exercise 3-19.)... 

Wood is built up of parallel columns of cells. Around these cells, cellulose embedded in lignin is wrapped. If wood is heated to temperatures above 600 °C (the exact temperature depends on the type of wood) in an inert atmosphere, then the polyaromatic biopolymers are broken down and what remains is a carbon skeleton with the anatomy of wood, both at a microscopic and macroscopic level. This skeleton facilitates the infiltration of, for instance, silicon and the reaction to silicon carbide. 

Compound B has a carbon skeleton different from the alcohol that produced it by dehydration. We are therefore led to consider a carbocation rearrangement. 

A compound possessing a carbon skeleton with certain side chains is not named as a derivative of another compound possessing a carbon skeleton with fewer side chains when the "added" one or more side chains in the first compound are identical to side chains present in the second compound. When the "added" side chains are not identical, the first compound, other things being equal, is named as a derivative of the second ... 

Thujane Group (Bicyclo Q3.1. O hexane Type). Name the thujane-type bicyclic terpene hydrocarbons (bicyclo 3.1. (T] hexane type) as thujanes, thujenes, and thu-jadienes, and base these names on the recommended fixed numbering of the thujane carbon skeleton. (Formula 46, Chart 10). For those derivatives which contain (1) fewer carbon atoms than thujane, (2) the same number as, or more carbon atoms than thujane but do not have a carbon skeleton identical to that of thujane, or (3) more carbon atoms than thujane and a carbon skeleton identical to that of thujane but contain substituents such that the principle of like treatment of like things will be violated by using the thujane, thujene, and thujadiene names, use the bicyclo 3.1 (T]-hexane-type names based on systematic bicyclo numbering (Formula 43, Chart 10). 

The preparation of 3-methvl-2-f3 7Ur-trimethvldodecvrithiophene. This compound, which has a carbon skeleton resembling that of phytane, is often a major component of certain immature sediments Q). Previous syntheses of this compound have used the acylation method whereby 3-methylthiophene is acylated with 3,7,11-trimethyldodecanoic acid (1, 8). Reference to Figure 5 indicates that the required compound will be accompanied by the 2,4-isomer and this is indeed the case. The pure compound can, however, be prepared using a lithiated alkylthiophene and an aldehyde (Figure 23). 

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