712
R. H. THOMSON
a C 5 unit. This is possible in PyroL· spp. Homoarbutin (C 7 ) and chimaphilin (Ci 2 ) both occur in P. incarnata, and pyrolatin is found in P.
O
OH
N
QH
MerT^^i
Mer^jr^^Me
Me 1
ΓΗ
Homoarbutin
Me^ c ^Me
(CLXXXII)
i 2
N
Me
C 6 H n 0 5 —O
Ö 2
Pyrolatin
japonica. The quinol (CLXXXII), similar to flavoglaucin, is not known
but is a possible precursor of chimaphilin, and a similar cyclization of
the C10 side chain of pyrolatin onto the benzene ring could lead to a
naphthoquinone of the alkannin type (LII). Of particular interest is
the co-occurrence of lapachol and 2-methylanthraquinone (tectoquinone) in Tectona grandis (Verbenaceae), and it is not difficult to
visualize the formation of the anthraquinone from the naphthoquinone
(25). Tectoquinone is accompanied in teakwood by 3-hydroxy-2-methylLapachol
Tectoquinone
anthraquinone (also found in the Rubiaceae), and it could be that the
numerous rubiaceous anthraquinones not readily accommodated by the
acetate theory are biosynthesized in this manner.