The monolignols are derived from the amino acid phenylalanine via the phenylpropanoid pathway involving various enzymes. Phenylalanine is first converted to paracoumaryl alcohol (H), which is subsequently elaborated to coniferyl alcohol (G) and sinapyl alcohol (S). This reaction happens in the  cytosol, while the polymerization of the monolignols occurs in the apoplast to which the monolignols have to be transported to though the cell membrane.
The monolignols are produced from phenylalanine via a pathway involving enzymes.  Phenylalanine is converted to paracoumaryl alcohol (H), which then undergoes further elaboration into coniferyl alcohol (G) and sinapyl alcohol (S). This occurs in the cytosol, while the polymerization of these monolignols happens in the apoplast, requiring transport through the cell membrane.