2-Methoxy-3-isobutylpyrazine has previously been reported to be an extremely potent flavoring material with a characteristic aroma of bell peppers. Twenty-one compounds structurally related to this molecule have been synthesized in an attempt to determine structural variations of the molecule which may be made and still retain the intense bell pepper note. For this flavor effect, the alkyl chain can vary from CB to at least CS; the effect is reduced by Cg. Replacing the methoxy group by ethoxy markedly reduces the effect, and it disappears with butoxy substitution. Adding a second alkyl function on the ring reduces the bell pepper character. The effect is not limited to the 2,3 isomer, since the 2,6 isomer possesses a similar note. A most surprising result is the fact that the oxygen of the methoxy group may be replaced by sulfur with little change in character.The compound having the characteristic aroma of bell peppers was identified as 2-methoxy-3-isobutylpyrazine (structure I, R1 = isobutyl) and was shown to possess an extremely low odor threshold (Buttery et al., 1969). Subsequently this compound was also reported in peas (Murray et al., 1970), in galbanum oil (Bramwell et al., 1969), and in coffee (Friedel et al., 1971). Due to the potency and unusual character of this compound, several reports have been published which describe the synthesis and odor properties of structurally related compounds (Seifert et al., 1970(Seifert et al., , 1972. This report extends the previous work for the purpose of further defining the basic chemical structure which is responsible for the intense bell pepper note.There are a number of ways of modifying the basic 2-methoxy-3-isobutylpyrazine molecule. The effect of varying alkyl chain length of R1 in structure I is one obvious choice. Other ways of varying the molecule include: investigating other positional isomers (structures I1 and VI); preparing the dialkyl-substituted methoxy compounds (111); replacing the methoxy by higher alkoxy (IV); and replacing the oxygen by sulfur (V and VI).Gas-Liquid Chromatography. Since the synthetic procedures described below result in a mixture of the 2,3-General Foods' Technical Center, White Plains, New York 10625. and 2,6-chloroalkylpyrazine isomers (Lutz et al., 1964), final purification of the desired isomer was achieved by gas-liquid chromatography. The samples were purified on a Ys in. X 6 ft column packed with 10% DEGS on 60/80 mesh Anakrom ABS in a Perkin-Elmer Model 900 gas chromatograph. Helium carrier gas flow was 30 ml/min and detection was by flame ionization. Temperature programming was utilized and the purified compound was trapped by condensation in a Dry Ice-cooled melting point capillary tube.General Synthetic Procedure. 2-C hloro-3-methylpyrazine containing a small amount of 2-chloro-6-methylpyrazine was prepared as described in the literature (Hirschberg and Spoerri, 1961;Lutz et al., 1964). This mixture was converted to the corresponding alkoxymethylpyrazine or thioalkoxy-methylpyrazine by reaction with the appropriate ...