108
3. Benzenoids
by Mathieson and Thomson (1971) from Temnopleurus toreumaticus. Gough
and Sutherland proved the structure of this juglone by using the deacetylation
reaction that had been introduced by Chang et al. (1964b) and by converting
the resulting trihydroxyjuglone to the more tractable 2,5,6,7-tetramethoxy-l,
4-naphthoquinone (60), which was identical with a synthetic sample (Natori
and Kumada, 1965).
Ο
OMe Ο
60
2,7-Dihydroxy-6-acetyljuglone (61) was one of the pigments isolated by
Moore et al. (1966a) from Echinothrix diadema and E. calamaris. It could be
identified with one of the known sodium borohydride reduction products
of 2,7-dihydroxy-3-acetylnaphthazarin (spinochrome A, 20 Moore et al,
1966b) and has since been synthesized (Singh et al, 1969).
Ο
Ο
CH 3 CO^Y^Y
CH 3 CO-\^Y^OH
OH
Ο
OH
Ο
61
62
The last of the juglones, 2,3,7-trihydroxy-6-acetyljuglone (62) was isolated
by the same workers (Moore et al, 1966a) from the same sea urchin spines
in a yield of 5 χ 10~
5 %. Although the pigment itself proved to be difficult
to handle (perhaps it had not been fully purified), the suggested structure 62
appeared to be the most likely one on the basis of the uv and nmr spectra
of the stable 2,3-dimethyl ether. This dimethyl ether was subsequently synthesized by Singh et al. (1969) and was identical with the naturally derived one.
Gough and Sutherland (1970) describe a synthesis of compound 62
starting with 2,3,7-trihydroxyjuglone (spinochrome B, 18) and arrive at a
product whose melting point, color, and one electronic spectral band differ
from those of the described pigment. Because the derived 2,3-dimethyl
ethers of the two products proved identical and natural material was no
longer available, the discrepancy remains. It may well be due to the fact that
the original observations prior to methylation (Moore et al., 1966a) were made
on an impure pigment. Gough and Sutherland's (1970) suggestion that the
original pigment is the 3-monomethyl ether of 62 is unsupported by the
molecular ion in the mass spectrum.
3. Benzenoids
by Mathieson and Thomson (1971) from Temnopleurus toreumaticus. Gough
and Sutherland proved the structure of this juglone by using the deacetylation
reaction that had been introduced by Chang et al. (1964b) and by converting
the resulting trihydroxyjuglone to the more tractable 2,5,6,7-tetramethoxy-l,
4-naphthoquinone (60), which was identical with a synthetic sample (Natori
and Kumada, 1965).
Ο
OMe Ο
60
2,7-Dihydroxy-6-acetyljuglone (61) was one of the pigments isolated by
Moore et al. (1966a) from Echinothrix diadema and E. calamaris. It could be
identified with one of the known sodium borohydride reduction products
of 2,7-dihydroxy-3-acetylnaphthazarin (spinochrome A, 20 Moore et al,
1966b) and has since been synthesized (Singh et al, 1969).
Ο
Ο
CH 3 CO^Y^Y
CH 3 CO-\^Y^OH
OH
Ο
OH
Ο
61
62
The last of the juglones, 2,3,7-trihydroxy-6-acetyljuglone (62) was isolated
by the same workers (Moore et al, 1966a) from the same sea urchin spines
in a yield of 5 χ 10~
5 %. Although the pigment itself proved to be difficult
to handle (perhaps it had not been fully purified), the suggested structure 62
appeared to be the most likely one on the basis of the uv and nmr spectra
of the stable 2,3-dimethyl ether. This dimethyl ether was subsequently synthesized by Singh et al. (1969) and was identical with the naturally derived one.
Gough and Sutherland (1970) describe a synthesis of compound 62
starting with 2,3,7-trihydroxyjuglone (spinochrome B, 18) and arrive at a
product whose melting point, color, and one electronic spectral band differ
from those of the described pigment. Because the derived 2,3-dimethyl
ethers of the two products proved identical and natural material was no
longer available, the discrepancy remains. It may well be due to the fact that
the original observations prior to methylation (Moore et al., 1966a) were made
on an impure pigment. Gough and Sutherland's (1970) suggestion that the
original pigment is the 3-monomethyl ether of 62 is unsupported by the
molecular ion in the mass spectrum.