X-Ray structure determination of methoxynepetaefolin and nepetaefolinol, labdane diterpenoids from Leonotis nepetaefolia R.Br.

Abstract

The gross structures previously assigned to methoxynepetaefolin (6) and nepetaefolinol (7) have been confirmed by X-ray crystallography, which also defined the stereochemistry at C-13 as (R) in (6) and (S) in (7). Crystals of (6) are monoclinic, space group P2₁, with a= 6.769(1), b= 11.551(2), c= 13.812(2), β= 96.15(1)°, and Z= 2. Crystals of (7) are orthorhombic, space group P2₁2₁2₁ with a= 8.910(2), b= 10.520(1), c= 19.527(2), and Z= 4. The structures were reined by least-squares to R 0.041 for (6) and 0.044 for (7).