Efficient synthesis of neurotrophic honokiol using Suzuki–Miyaura reactions

Efficient synthesis of honokiol (1) was accomplished using two kinds of Suzuki–Miyaura reactions. The first Suzuki–Miyaura reaction was employed to couple 2-bromophenol (6) with 4-hydroxyphenylboronic acid (5), giving rise to biphenol 4, and the second coupling was used to introduce allyl groups at 5- and 3′-positions of honokiol. The total synthesis of 1 was completed in 74% yield over five steps from 6, or in 83% yield over four steps from biphenol 4.