Camphor, optically active, formed from

Calcium D-galactonate, I, 70 Calcium D-gluconate, III, 141, 142, 149, 152, 155, 156, 161 IV, 331 Calcium hypochlorite, III, 165 Calcium 2-keto-D-gIuconate, III, 148, 155 Calcium 5-keto-D-gluconate, III, 156 Calcium lactobionate, calcium bromide double salt, III, 155 Calcium Ievulinate, IV, 311 Calcium maltobionate, III, 161 Calcium D-mannonate, III, 152 Calcium pectate, I, 334 Calcium D-rhamnonate, III, 144 Calcium salts, in preparation of aldonic acids with NaCN, I, 23 Calcium vicianobionate, III, 154 Calcium D-xylonate, III, 155 Camphor, optically active, formed from inactive (racemic) camphor carboxylic acid in the presence of quinine, quinidine or nicotine, V, 53 Camphor carboxylic acid. See Camphor. Camphor, 3-hydroxy-, IV, 89 Camphorquinone, phytochemical reduction of, IV, 89... 

Further evidence for the formation of intermediate compounds in catalytic reactions is afforded by the observation (a) that optically active camphor is formed from optically inactive (racemic) camphor carboxylic acid in the presence of the d- or /-forms of quinine, quinidine or nicotine and (6) that optically active bases, e.g., quinidine, catalyze the synthesis of optically active mandelonitrile from benzaldehyde and hydrocyanic acid.10 These results hardly admit of any other interpretation than the intermittent production of a catalyst-reactant compound. 

The 3-hydroxy-K end group is characteristic of capsorubin (28), and other carotenoids isolated from paprika (Capsicum annuum). All syntheses are based on the Cio + C2o + Cio = C4o strategy, and use crocetindialdehyde (27) as central building block and the aldol condensation as the coupling reaction Scheme 6). The synthesis of optically active capsorubin (28), reported in 1973, was the first synthesis of an enantiomerically pure xanthophyll [11]. For the optically active form of the key building block, the frans-Cio-hydroxyketone 26, two approaches have been reported. In the first reaction sequence, (+)-camphor (143) was converted into camphoric acid (144) by treatment with nitric acid. Camphoric acid (144) was then esterified with dimethyl sulphate... 

For the synthesis of carotenoids in optically active form, compounds ex chiral pool have been used extensively as starting materials, the synthesis of capsorubin (413) from (+)-camphor being one of the most prominent examples (see Chapter 3 Part ni.E). In the following examples, the preparation of chiral building blocks for the synthesis of chiral carotenoids starting from an amino acid and a terpene is described. 

Camphor was originally obtained from the camphor tree Lauras eamphora in which it appeared in the optically active dextro-rotary form. Since about 1920 the racemic ( ) mixture derived from oil of turpentine has been more generally used. By fractional distillation of oil of turpentine the product pinene is obtained. By treating this with hydrochloric acid, pinene hydrochloride (also known as bomyl chloride) may be produced. This is then boiled with acetic acid to hydrolyse the material to the racemic bomeol, which on oxidation yields camphor. Camphor is a white crystalline solid (m.p. 175°C) with the structure shown in Figure 22.3. 

The [2,3] Wittig rearrangement151 of the optically active tertiary allyl ether 10 derived from ( + )-camphor yields the two olefin products 11 and 12 in a 70 30 (EjZ) ratio. The configuration around the double bond was established by NOE studies. The configuration at the newly formed carbinol center could also have been determined by spectroscopic means, but was assigned by a correlation sequence (see p 475)152. 

In special cases of optically active photochromes the change in molecular form is accompanied by a change in specific rotation. Singh (170) noted that as (l-naphthylamino)camphor (0.726 g. in 100 cc. chloroform) turned from colorless to green with a 6-min. exposure to sunlight, the specific rotation changed from 126° to 186.6°. Reversal of the system required days. 

Camphor occurs in nature is optically active (d andZ-forms), whereas the synthetic camphor is in racemic from. The following optical rotations were reported for (+)-Camphor. 

Alan Baxter lost his bronze medal in the winter Olympics in 2000 because he used an American Vick inhaler and not a British one.1,2 Note the position of the CH3 attached to the central carbon atom (Figure 2.18). The British Vick inhaler contains a mixture of menthol, camphor and methyl salicylate the American Vick inhaler also contains L-methamphetamine. This is used as a decongestant and has no performance-improving properties, whereas its optically active isomer D-methamphetamine (commonly known as speed ) is a prohibited drug and is a performance improver. However, the Olympic Committee does not distinguish between these two isomers in its detective work and chemical analysis. It therefore reported that his urine contained methamphetamine and did not report that it was the ineffective l form. The committee took the medal away from him. If they only had known their chemistry and all about optically active isomers. 

Preparative Methods Co(a-cqd)2 is prepared from Cobalt(II) Chloride hexahydrate and the corresponding isomer of cam-phorquinone dioxime (cqd) (from optically active natural camphor) in ethanol with addition of an aqueous solution of NaOH under nitrogen or argon. This complex is best when freshly prepared before use under nitrogen or preferably under argon. The starting material, L-camphor, is easily obtained in optically pure form. 

Phenylbenzylethyl-n-propylarsonium iodide, (CgHj)(CeH5CH2) (C2H6)(C3H7)AsI, is formed firom phenylethyl- i-propylarsine and benzyl iodide by heating at 40° to 50 C. It separates from dilute alcohol in colourless crystals, M.pt. 128° C. Its d-camphor- -sulphonate shows no signs of resolution into optically active components. 

Apart from natural camphor, the synthetic material is now made in considerable quantities. Natural camphor is optically active, the synthetic product is the racemic form, and is inactive except for small quantities of impurities. 

Ketalization of myo-inositol (1), which is also a symmetrical substance, was carried out with D-camphor dimethyl ketal 179 producing several products, from which after partial hydrolysis of the trans-ketal a diastereomeric mixture of four 1,2-cis-ketals 65a, b, c, and d were obtained (Scheme 4-4).31 When a mixture of the initially formed ketalization products was exposed to acidic conditions in a solvent system of CHCI3, MeOH, and H2O, the major monoketal 65a was obtained preferentially, resulting from the precipitation after decomposition of the trans-ketals and equilibration. The latter procedure provides a practical method for the preparation of a chiral 1,2-protected myo-inositol which can be transformed into various optically active inositol derivatives.1 7 3... 

The Use of Optically Active Starting Materials.—This is arguably the most satisfying strategy to adopt in synthesizing optically active compounds, and a number of examples have already been given in this chapter. Others noted have been the synthesis of (-)-(15,7S)-exo-brevicomin (30) from ( + )-(2i ,3i )-diethyl tartrate by Meyer, a synthesis which may be compared to and contrasted with a short photochemical route to racemic exo-brevicomin (30) by Chaquin et al. The ( + )-and (—)-forms of camphor have often been used as optically active starting materials... 

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