合成路线1

Nitration of chromanone (I) with fuming HNO3 at -35 C afforded 6-nitro-4-chromanone (II). Subsequent aldol condensation of (II) with glyoxylic acid (III) in the presence of H2SO4 produced the alpha-beta-unsaturated acid (IV). Further hydrogenation of the nitro, keto, and olefin groups of (IV) with concomitant esterification produced the benzopyranylacetate (V). After protection of (V) as the N-Boc derivative (VI), optical resolution was achieved by preparative HPLC on a Chiralcel-OD column. The desired (S)-enantiomer (VI) was deprotected using ethanolic HCl to afford amine (VII), which was condensed with 4-cyanobenzoyl chloride (VIII) to give amide (IX). Treatment of (IX) with HCl-EtOH produced imidate (X), and subsequent treatment with morpholine (XI) furnished the target amidine, which was isolated as the hydrochloride salt.