3. Results
Citral, [2-(E), (Z)-3,7-dimethyl-octa-2,6-dienal] (1a,a), is a monoterpene
aldehyde which is the major component of lemon grass oil
extracted from C. citratus belonging to Gramineae [14–16] as a mixture
of (2E)-and (2Z)-isomer at a ratio of 3:2, respectively.
Thermal oxidation of citral using m-choroperbenzoic acid
(mcpba) in chloroform at room temperature or photochemical oxidation
with hydrogen peroxide using a sodium lamp, we obtained
a mixture of (E & Z)-epoxides 2a & 2a0 in ca. 60% yield (in the ratio
of 60:40 of E:Z configuration). No other products were observed.
[13] (Scheme 1).
Epoxides could be reacted with DNA producing a major adduct
[12]. Therefore, the mixture of epoxides 2a & a0 was condensed with
2 mol of cytosine to give the adduct 3 through condensation
between aldehyde group and amino group in the first mole of
cytosine to give intermediate X1, while the other molecule of cytosine
was added to amino group on the epoxide ring and open it
producing intermediate X2 which cyclized to give adduct 3 (Scheme
2). The 1H-NMRspectrum of 3 contained a doublet at d 0.90 ppmdue
to protons of CH3 group and a singlet at d 1.30 due to protons of other
two CH3 groups, and three doublets at d 7.54, 7.71 and 7.72 ppm due
to protons of two methylene groups in cytosine ring. Mass spectrum
showed the molecular ion peak (M+2H) at m/z 370.
Fungal and bacterial diseases are among the most common
infections, and causative organisms include dermatophytic, yeasts