7-Hydroxy-2-methyl-anthraquinon

Quinones Anthraquinones 1 -Hydroxy-2 -methyl -anthraquinone Schweppe Winter (1997)... 

The sulfonic group present in anthraquinonc dyes is readily replaced by the Mannich reagent, as has been mentioned previously (see 10 in Sec. A. I) in particular, 1 -amino-and l-hydroxy-2-anthraquinone-sulfonic acids may occasionally be involved in the production of cyclic Mannich bases. Finally, the methyl group of dimelhylsulfite (CH,)2SOj may be similarly replaced by the dimethylaminomcthyl group giving OjS—CH —... 

D-Glucosides of several hydroxyanthraquinones have been reported. For example, Schunk and Marchlewski isolated rubiadin D-glucoside from madder root. This compound was later synthesized by Jones and Robertson and shown to be 3-(/3-D-glucopyranosyloxy)-l-hydroxy-2-methyl-anthraquinone. 

Carniinic acM (7-C-glucopyranosyl-3,5,6,8-tetra-hydroxy-1 -methyl-anthraquinone-2-carboxylic acid, E 120, C. I. natural red 4, C. 1. 75470). 

Sequential applications of these methods yield naturally occurring anthraquinones, eg, macrosporin [22225-67-8] (86) in 83% yield from 2-chloro-6-methyl-7-hydroxy-l,4-naphthoquinone [76665-67-3] (87), which is produced in 78% yield from (26) (84). 

Further reduction of quinones - acquisition of four or more hydrogens per molecule - was achieved with lithium aluminum hydride which reduced, in yields lower than 10%, 2-methyl-1,4-naphthoquinone to 1,2,3,4-tetrahydro-l,4-dihydroxy-2-methylnaphthalene and to l,2,3,4-tetrahydro-4-hydroxy-l-keto-2-methylnaphthalene [931]. Lithium aluminum hydride [931], sodium borohydride, lithium trie thy Iborohydride and 9-borabicyclo[3.3.1Jnomine [100] converted anthraquinone to 9,10-dihydro-9,10-dihydroxyanthracene in respective yields of 67, 65, 77 and 79%. 

Most of the previously identified 25 chlorinated anthraquinones are found in lichen and fungi (1). The newly discovered examples have a wider range of sources. Studies of the lichen Nephroma laevigatum from the British Columbia coast have identified the new anthraquinone, 7-chloro-l-O-methyl-co-hydroxy-emodin (2157), and the two novel hypericins, 7,7 -dichlorohypericin (2158) and 2,2, 7,7 -tetrachlorohypericin (2159) (1931), as well as 5-chloroemodin (2160), 5-c h I oro -1 - (9 - m e t h v I - o >- h yd ro x ye m od i n (2161), and 5-chloro-co-hydroxyemodin (2162) (1932). In addition to containing several known chlorinated anthraquinones, the Scandinavian fungus Dermocybe sanguinea has afforded the new 5,7-dichloroendocrocin (2163) (1933). The novel tetracyclic anthraquinones... 

The X-ray structures of two anthraquinone derivates of 1,3-dioxane were published. In both 1 -methoxy-4-(2-methylprop-2-enyloxy)-2-[(2i ,6i )-4,4,6-trimethyl-1,3-dioxan-2-yl]-anthraquinone and 4-hydroxy-3-(2-methyl prop-2-enyloxy)-2-[(27 ,67 )-4,4,6-trimethyl-l,3-dioxan-2-yl]anthraquinone the 1,3-dioxane ring adopts the chair conformation and the substituents in positions 2 and 6 are in equatorial conformations (99AX(C)436). Finally, Freeman et al. (02JMS(T)43), employing both ab initio theory and density function theory, calculated the energies of chair, half-chair, sofa, twist, and boat conformers of 1,3-dioxane. 

Cyclic amines with a great variety of A-substituents have been described, many with biologically significant groups, e.g., imidazolyl. Others include methyl-phosphonic and -phosphinic acids,147 methyl-sulfonate,148 quinolin-2-ylmethyl, anthraquinon-2-ylmethyl, 2-(3-hydroxy-pyridyl)methyl, 2-methoxyethyl,149 2-methylthioethyl,150 thiophenyl, pyrazolyl, etc. 

Kuo et al., [18] investigated the structure-activity relationships of anthraquinones on intestinal motility, using rabbit small intestinal strips. This study revealed the critical requirement of a hydroxy group at 2 position, whereas the presence of other polar groups at this position, such as an amino, aldehyde and carboxylic acid groups, significantly reduced the activity. The presence of a methyl group and esterification of the carboxylic acid at 2 position was found to abolish the activity. 

Rubiaceaous plants are usually rich in anthraquinones. The first four anthraquinones, 2-methyl-3-methoxyanthraquinone (7), 2-methyl-3-hydroxyanthraquinone (8), 2-methyl-3-hydroxy-4-methoxyanthraquinone (9) and 2,3-dimethoxy-6-methylanthra-quinone (10) reported in genus Hedyotis were isolated from H. diffusa [26]. All the compounds except for (10) are substituted only in ring C. The structure of (10) has been later confirmed by synthesis based on Diels-Alder reaction. This anthraquinone has been the only one reported from a natural source until today. Other anthraquinones possessing the same substitution pattern are synthetic products [27]. 

In recent years atrochrysone (4) and several other pre-anthraquinones have been isolated from fungi and higher plants (Scheme 2). The parent compound 4 occurs in the toadstools Cortinarius atrovirens and . odoratus (ref. 3). The monomethyl ethers torosachrysone (7) (ref. 4) and asperflavin (8) (ref. 5) are produced by Cassia torosa and Aspergillus flavus, respectively. Torosa-chrysone-8-O-methyl ether (9) has been found in fruitbodies of several toadstools along with its trans-4-hydroxy derivative 10 (ref. 3). Further compounds of this type, e.g. vismione A (11) and B (12), have been isolated from Vismia species (ref. 6). With the only exception of 7, the absolute configuration of these pre-anthraquinones remains unknown. 

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