by

acetate 1pentane 1: 1L* A reddish colour develops instantaneously when the freshly
developed TLC plate is sprayed with 1% vanillin in aqueous sulfuric acid (reagent A) and
then carefully heated on a hot plate. When the compound is very concentrated a reddish
colour develops initially. then darkens and slowly turns into a permanent greyish blue
coloration.
Impure arthrosporone is usually obtained as a yellowish gum. It is then subjected to
two or three purifications using a combination of flash and normal chromatographic
techniques (solvent systems acetonitrile 1dichloromethane 1:3: acetone 1dichloromethane
1585).
Arthrosporone is obtained as shiny crystals which are recrystallized from
Skellysolve B/diethyl ether to give analytically pure compound 20 m.p. 139-141·C.. [al O lJ
= 140.8 (CHCI J ). Arthrosporone has a molecular formula CUHl.O J • accounting for a
molecular weight of 252 as determined by a high resolution mass spectrum (HRMS). The
molecular weight (mol. wt.l was confirmed by a chemical ionization (CI) mass spectrum; the
peak at ml z 270 (100%. M+ 18) corresponding to a collision complex of arthrosporone
and an ammonium ion (NH.-). The fragmentation pattern in the HRMS of 20 displays peaks
100.0%)
The ultraviolet (UV) spectrum of arthrosporone CÀ 280 nm) shows a band
max
characteristic of the n-+1l'* transition of a ketone. JO The Fourier transform infrared spectra
(FTIR) of compound 20 shows strong bands at 3440 cm- l (broad. OH), 1731 cm- l (C=O)
and a moderately intense doublet at 1380 and 1360 cm- l • The doublet is characteristic of
gem-dimethyl groups (C-H bending vibration).J' From this spectral information it was
concluded that this metabolite is a ketone (possibly a cyclopentanone)Jl and thus it was
named arthrosporone (a ketonlC metabolite from Arthrosporael. Compound 20 has four
sites of unsaturatlon, at least one hydroxyl group (MS, IRI and a geminal dimethyl group
(IR).
"The R' f is the Rf using cholesterol as reference.
15