100
3. Benzenoids
Ο
OH
OH
Ο
1
Y^OMe
Cl^^^Y^OMe
°
OMe
OH
Ο
27
28
29
spinochrome D (24) intermediate, and 2,3-dimethoxy-6,7-dichloronaphthazarin (30), the intermediate for spinochrome Ε (17). Moreover the leucoacetate of spinochrome D (31) was acetylated with acetic acid and boron
trifluoride, furnishing spinochrome C (14) after hydrolysis in the presence of
air.
OH
Ο
OAc OAc
III
JmX
C l ^ Y ^ Y ^ O M e
A c O ^ Y ^ Y ^OAc
OH
Ο
OAc OAc
30
31
Finally, spinochrome A (20) was synthesized from methoxynaphthazarin
(32), as outlined in Scheme 3.1, via the diquinone 33, 7-methoxy-2-hydroxynaphthazarin (34), l,2,4,5,8-pentaacetoxy-7-methoxynaphthalene (35), and
2,7-diacetyl-3,6-dihydroxynaphthazarin (36). Removal of one of the acetyl
groups in 36 furnished 20. Details of these syntheses were published in a full
paper (Singh et al, 1968a).
OH
Ο
Ο
Ο
OH
Ο
OH
Ο
Ο
Ο
ΟΗ
Ο
32
33
34
OAc OAc
OH
Ο
MeO^A^Js^OAc
CHaCO^^k^^JL^COCHa
Ac a o,KOAc )
I Ο Ι Ο Ι
J
B^
£ *
L I
ll
20
Pd-c,H a
ΗΟ^^Γ^Γ^ΟΗ
OAc OAc
OH
Ο
35
36
SCHEME 3.1