Crystal structures of two 1,2,3,4-tetra-hydro-naphthalenes obtained during efforts towards the total synthesis of elisabethin A

Abstract

The two substituted 1,2,3,4-tetra-hydro-naphthalenes, methyl (R)-3-{(1R,4S)-6-meth-oxy-4,7-dimethyl-5,8-bis-[(triiso-propyl-sil-yl)-oxy]-1,2,3,4-tetra-hydro-naph-th-al-en-1-yl}butano-ate, C₃₆H₆₆O₅Si₂, (2), and methyl (E)-3-{(1R,4S)-8-hy-droxy-6-meth-oxy-4,7-dimethyl-5-[(triiso-propyl-sil-yl)-oxy]-1,2,3,4-tetra-hydro-naphthalen-1-yl}acrylate, C₂₆H₄₂O₅Si, (8), crystallize in the Sohncke space groups P2₁2₁2₁ and P2₁, respectively, with the absolute structure determined on the basis of anomalous dispersion effects. The configurations of the stereo centres in the 1,2,3,4-tetra-hydro-naphthalene moiety of (2) and (8) are the same, and the conformation of the non-aromatic part of the ring system is nearly identical. In the crystal of (2), weak non-classical C-H⋯O inter-actions consolidate the packing, whereas in (8), inter-molecular O-H⋯O hydrogen-bonding inter-actions of medium-to-weak strength direct the mol-ecules into Z-shaped strands extending parallel to [010].

Keywords: absolute configuration; crystal structure; disorder; fused ring system; marine diterpenoids.