by

H appears as a doublet (J = 14Hz) and H h is a doublet of doublets (J = 14
9 gem gem
Hz, J . = 3 Hz). The multiplicity of H (triplet) and H (doublet) suggests that
VIC J 9
arthrosporone does not have an ethylenic (-CH,CH,-) linkage in its structure. Therefore the
part structure Il is rejected. From the information gathered thus far, the structure of
arthrosporone incorporates the partial structures 1. III or IV, and V to VII (Table 2).
The number of hydrox yi proton(s) in compound 20 could not be obtained since
these protons resonate at the same chemical shift as that of residual water in
deuterochloroform, Analysis of the lH NMR spectrum of arthrosporone allows the
assignment of 22 (of 24) hydrogens, which are directly attached to carbon, Therefore the
structure of arthrospc>rone must contain two tertiary hydroxyl groups.
The tertiary nature of the hydroxyl groups was consistent with their resistance to
oxidation reactions, However, under forcing conditions arthrosporone could be
selectively converted to a monoacetyl derivative. Acetylation l • of arthrosporone with
acetic anhydride containing a trace of 4-N,N-dimethylaminopyridine in triethylamine at
room temperature for three days, gave a monoacetate 27 (m.p. 120- 122'C, [al D 'l -37.6',
m/z calcd. for C]7H 160., 294,1824; found 294.1818), The infrared spectrum of 27
shows a weak intensity broad band at 3400 cm- l (OH), and strong bands st 1736 and 1243
(OAC) cm'}, The lH NMR spectrum of the monoacetate 27 shows a 3-proton singlet at é
1.98 attributed to an acetyl methyl and a D,O exchangeable broad singlet at 0 1.47 due to
a hydroxyl proton. The presence of a hydroxyl group as evidenced by the infrared and
lH NMR spectra of the monoacetate 27 confirms the presence of two hydroxyl groups in
the structure of arthrosporone. This information suggests that arthrosporone is a
ketodiol,
The llC NMR spectrum of arthrosporone exhibits the presence of 15 carbons. The
signal at 0 216.4 is the only sp'-hybridized carbon and is assigned to the carbonyl carbon
of the cyclopentanone ll (partial structure VIII). Two signais appearing at 691 .O(s), 87.0(sl
are assigned to the two spl-hybridized qua,ternary carbons bearing the hydroxyl groups.H
The rest of the spectrum shows the presence of two spl-hybridized quaternary carbons
(singletx2), two methine (doubletx.2), four methylene (tripletx4l and four methyl (quartet x
18