38
/. Isoprenoids
4. A NORTRITERPENOID
Although the group of antibiotics known as the cephalosporins are sometimes listed among marine natural products (e.g., Baslow, 1969) it is questionable whether these compounds are in fact of marine origin. Such a compound,
a nortriterpenoid of somewhat dubious marine ancestry, is cephalosporin
Px (92). It will be briefly mentioned here, but will be omitted from Table 1.3,
21
LC0 2 H
H
i l
13|
jl6
ÖAc
92
which lists the marine triterpenoids. According to Crawford et al (1952),
who first cultured the organism that produces it, the antibiotic was first
isolated by Brotzu in 1948 from a microorganism, Cephalosporium sp.,
perhaps C. acremonium, that was collected near a sewage outfall off the coast
of Sardinia. Early structural work (Burton et ai, 1956) indicated a steroidal
character of C 32 composition. Mass spectral (Halsall et al., 1963) and nmr
(Mêlera, 1963) data produced a revised molecular formula of C 3 3H 5 9 0 8
with an additional quartenary methyl group. Definitive structural work by
several groups (Halsall et al., 1966; Oxley, 1966; Chou et al, 1967, 1969) led
to structure 92 for cephalosporin P x closely related to helvolic (93) and
L C0 2
H
Γ 21
Jl
JOAc
H I I
I _ I I
J [13 |16
~ H
J
HO93
94