304
MAURICE WELSCH
acids, all produced by lichens, and ungulinic acid (XCV), from the
basidiomycete Polyporus betulinus.
The mold-produced tetronic acids, carlosic (XCVI) and carolic
(XCVII), have been shown, by isotope studies, to be formed from the
condensation of a 6-carbon atom chain, derived from acetate, respectively, 3-ketohexanoic and 3-keto-6-hydroxyhexanoic acid, with an acid
V
H
H 2 C
CH 2
ι
Ο
I
\
ι
II
Ο—\ C—O
H O I . C- CH 2
—CH 2
— CH 3
\ j /
HOOC-H 2 C-^0^0
H 3 C^O^O
'
I
Carlosic acid
Carolic acid
(XCVI)
(XCVn)
I
HOOC
ι CH 3
ι
Lichesterinic acid
(XCVIII)
HOOC.
1
^CH.
H 27 C 13 Ο -Ο
Protolichesterinic acid
(XCK)
Acetomycin
Antibiotic PA-147
(C)
(CI)
of the Krebs cycle, malic or oxaloacetic for the former, lactic or pyruvic
for the latter (261a). By analogy, it is assumed that the lichen-produced
Z-lichesterinic (XCVIII) and protolichesterinic (XCIX) acid, of which
the d and hallo isomers are known, are formed from pyruvate and
3-oxypalmitate.
The mode of formation of two, obviously related, streptomycete