Constitution of compound

A careful assessment of the constitution of compound 10 led to the development of a rather efficient strategy featuring the Diels-Alder reaction (see Scheme 3). Although the unassisted intermole-cular reaction between 3-hydroxy-2-pyrone (16)23 and a,/ -unsatu-rated ester 17 is unacceptable in terms of both regioselectivity and chemical yield, compounds 16 and 17 combine smoothly in refluxing benzene and in the presence of phenylboronic acid to give fused bicyclic lactone 12 (61% yield) after workup with 2,2-... 

In an effort to make productive use of the undesired C-13 epimer, 100-/ , a process was developed to convert it into the desired isomer 100. To this end, reaction of the lactone enolate derived from 100-) with phenylselenenyl bromide produces an a-selenated lactone which can subsequently be converted to a,) -unsaturated lactone 148 through oxidative syn elimination (91 % overall yield). Interestingly, when 148 is treated sequentially with lithium bis(trimethylsilyl)amide and methanol, the double bond of the unsaturated lactone is shifted, the lactone ring is cleaved, and ) ,y-unsaturated methyl ester alcohol 149 is formed in 94% yield. In light of the constitution of compound 149, we were hopeful that a hydroxyl-directed hydrogenation52 of the trisubstituted double bond might proceed diastereoselectively in the desired direction In the event, however, hydrogenation of 149 in the presence of [Ir(COD)(py)P(Cy)3](PF6)53 produces an equimolar mixture of C-13 epimers in 80 % yield. Sequential methyl ester saponification and lactonization reactions then furnish a separable 1 1 mixture of lactones 100 and 100-) (72% overall yield from 149). 

Balaiah V, Seshadri TR, Venkateswarlu V (1942) Visible fluorescence and chemical constitution of compounds of the benzopyrone group. Part III. Further study of structural influences in coumarins. Proc Ind Acad Sci 16A 68-82... 

Muller and Varga7 also tried unsuccessfully to clarify the constitution of compound XXVI, using lead tetraacetate in the oxidation, but they were unable to isolate any product. 

As the number of known coordination compounds increased, theories to explain their constitution were devised.35 Thomas Graham (1805-1869) is credited with originating the first theory of metal ammines, the so-called ammonium theory, in which metal ammines are considered as substituted ammonium compounds. Graham attempted to explain the constitution of compounds such as diamminecopper(II) chloride by the formula (1). 

Three main methods are available for describing the constitution of compounds one can draw structures, write names or write formulae. A drawn structure contains information about the structural components of the molecule as well as their stereochemical relationships. Unfortunately, such structures are not usually suitable for inclusion in text. Names and formulae are therefore used to describe the constitution of a compound. 

Most importantly, Wurtz asserted that the main lines of Couper s theory were not, despite his protestations, irreconcilable with either radical or type theory, considering especially the most recent modifications of those theories. "In general," he wrote, "1 find M. Couper s formulas too arbitrary, too distant from experiment." Rational formulas are not intended to show the "intimate constitution of compounds," only reactions "hence their advantage." In sum "It is too much of hypotheses, and it is wrong to present these things as if they were handed down by God. In this respect M. Kekule, who seems better to have understood the sense and import of the ideas which he was the first to express, wisely wrote at the end of his memoir, As for me, I attach but a secondary importance to considerations of this sort. " Wurtz failed to take this opportunity to affirm that he had Couper s paper in hand at the time Kekule s second theoretical paper was published. In several subsequent historical accounts of the rise of structure theory, Wurtz mentioned Couper s independent formulation only once, and that in a footnote. It does appear that Wurtz and Couper had clashed personally, and this may have ever after influenced Wurtz s treatment of his former student. His reticence fully to acknowledge Couper s substantial accomplishment is out of character for Wurtz s notably wise and generous personality. 

The idea of atomicity. . . was employed by Frankland to explain the nature of the organometallic bodies, and its application was further extended by Kolbe to a large number of organic substances. It is, however, to Kekul that we owe the complete generalization of this idea and its systematic application to all classes of compounds. This first rendered it possible to represent, as it is often advantageous to do, the constitution of compounds by completely dissected formulae. The most convenient way of doing this is to employ some suitable system of graphic notation. 

I am glad to see that we agree on structural formulas. The main distinction of my views on the chemical constitution of chemical compounds from those of the true structural chemists is that the latter deny the real existence of compound radicals in compounds. For these people, methyl, ethyl etc. do not really exist in compounds, but rather are only ideal, conventional quantities.. . . You have misunderstood. . . when you say that I reproach young chemists for using constitutional formulas. What I condemn is the modern doctrine of bonds which does not assume the existence of compound radicals, and by which immature chemists are misled to believe that they are capable of explaining the constitution of compounds without the help of exact chemical research. ... 

The term simple amphiphile describes the principle of molecular constitution of compounds which will be discussed in this section. The simplest molecular architecture of an amphiphile consists of a hydrophilic group connected to a lipophilic substructure as shown in Fig. 4. 

Taking Le Febvre s philosophy of compounds and principles as an example, we have discussed the Paracelsian view of the invisible constitution of compounds at... 

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