Melts ultraviolet absorption spectra

The unmodified form of coelenterazine, C26H2i03N3(mass spec. M+ 423), can be crystallized from methanol as orange-yellow prisms with a melting point of 175-178°C (dec). In methanol, coelenterazine is fluorescent in yellow, and its ultraviolet absorption spectrum shows a maximum at 435 nm (s 9,800), as shown in Fig. 5.1. 

Mycoside A.—This compound haa been obtained as a nearly colorless solid, melting at 105°, [a] -37° (CHCl,) C, 72.2 H, 11.3 OCH, 8.6 N, 0 P, 0%. The ultraviolet absorption spectrum shows maxima at 222, 274, and 278 m/i (in hexane). Mycoside A contains three different 0-methylated 6-deoxyhexoses, which have been identified as 2-0-methyl-fucose, 2-0-methylrhamnose, and 2,4-di-0-methylrhamnose. The lipid moiety of mycoside A is a di- or tri-mycocerosate of an aromatic alcohol. 

It is possible (although not necessary) to recrystallize 5 -FSBA from dimethylformamide, as described by Pal et al. The resultant product contains 1 mole of dimethylformamide in the crystal and exhibits a melting point of 159°-160°. This form of the compound exhibits the same features for the ultraviolet absorption spectrum, but with somewhat different extinction coefficients (ease nm = 1-58 X 10 cm- 232 nm = 2.17 X 10" cm-i M-i). 

It has a characteristic ultraviolet absorption spectrum in aqueous solution (535,628). In water, phalloidin gives a neutral solution. Various derivatives can be prepared from it, in particular an acetyl derivative crystallizing as prisms from aqueous acetone, and melting with decomposition at 203-205° C. 

Bis(4-imino-2-pentanonato)nickel(II) crystallizes from a benzene-petroleum ether mixture as dark red needles or as fine red-orange needles. The two forms have identical melting points. The compound is very soluble in chloroform, but less soluble in benzene, pyridine, and carbon tetrachloride, and very insoluble in water. The compound crystallizes from pyridine without adduct formation. The compound is diamagnetic and apparently has the trans configuration. Partial resolution in optically active fractions has been achieved by means of a chromatographic technique. Molecular weight determinations indicate that the compound is monomeric in chloroform and benzene solution. The visible absorption spectrum of this compound in chloroform is characterized by a band centered at 552 m/i (e = 43). The ultraviolet absorption maxima for solutions in 1 1 benzene-petroleum ether occur at 298, 348, and 364 m x (e = 4150, 4760, and 4460, respectively). ... 

Actinomycin A, thus prepared, is in the form of bright red crystalline platelets, melting at 250° with decomposition. The pigment is easily soluble in chloroform, benzene, or ethanol, less soluble in acetone and hot ethyl acetate, and slightly soluble in water and ether. Actinomycin A is levorotatory [ ]d = —320° (c = 0.25% in ethanol). It possesses a characteristic absorption spectrum in visible and in ultraviolet light (612), with maxima at 4500 A and between 2300 and 2500 A. 

The product is reported to melt at 102°. This material has n.m.r. peaks (CDCI3 solution) at 2.14 and 6.19p.p.m. with relative intensities of 3 1. The infrared spectrum (CHCI3 solution) shows the strongest absorption at 1670 cm accompanied, among others, by four more bands at 1390, 1280, 1005, and 835 cm. The product has ultraviolet maxima (CHCI3 solution) at 260 m (c 2600), 400 m/i (e 1120), and 572 rn/i (e 288). It is reported that the material undergoes slow Diels-Alder dimerization. ... 

Upon exposure to thermal energy, absorption of light, or involvement in specific chemical reactions, interconversion of lycopene isomers is known to take place. The cis isomers of lycopene, formed by rotation around any of its conjugated double bonds, have chemical and physical characteristics distinctly different from their all-frans counterparts. Some of the differences resulting from trans-to-cis isomerization include lower melting point, decreased color intensity, a shift in the lambda max, smaller extinction coefficients, and the appearance of a new maximum in the ultraviolet spectrum. ... 

Pilocarpine and isopilocarpine are usually obtained as colorless, viscous oils, but both have been crystallized as low-melting, hygroscopic solids (39, 50). Pilocarpine is triboluminescent (93). It is readily soluble in water, alcohol, and chloroform (28, 78, 50), fairly soluble in benzene (50), and almost insoluble in ether or light petroleum (28). Isopilocarpine is very similar in its solubility (28, 50). Pilocarpine base, in alcoholic solution, shows an absorption maximum of low intensity at 2630 A (94) in pilocarpine salicylate the bands of salicylic acid dominate the spectrum. The absorption in the ultraviolet of solutions of the nitrates of the alkaloids, recorded by Jowett (33), appear to be due solely to the nitrate ion. The infrared absorption spectra of pilocarpine and its hydrochloride have been examined (95). 

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