T

N XH3

RCH0 -H20

H3CyN CH2R alkylpyrazines

NyCH3 N CH3

NyCH3 N CH3

2,3-dimethyl-5-(2'-methylpropyl)pyrazine

Figure 9.15 The probable biosynthetic route to alkylpyrazines. The trisubstituted pyrazines have been converted to tetrasubstituted hydroxylated or unsaturated examples in the laboratory by addition of isopentanal, followed by NaBH4 reduction and sometimes dehydration. All such compounds are found in nature. 2,3-Dimethyl-5-(2'-methylpropyl)pyrazine seems to have a different biosynthetic origin

H3Cn h3c

H3cv

CH3 X ~ h2n cooh leucine cho x h2n cooh

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