Crystal and molecular structure of tamaulipin-A, a trans,trans-germacra-1(10),4-dienolide sesquiterpene lactone

Abstract

The crystal and molecular structure of tamaulipin-A (I), C₁₅H₂₀O₃, has been determined by single-crystal X-ray diffraction. Crystals are orthorhombic, space group P2₁2₁2₁, a= 7.890(9), b= 11.957(13), c= 14.649(17)Å, Z= 4. The structure was solved from diffractometer data by direct phasing techniques and refined by full-matrix least-squares to R 8.1% over 732 reflections. The cyclodecadiene ring is in the chair–chair conformation, the methyl groups attached to C(4) and C(10) are in the syn-β-orientation (absolute configuration inferred from independent data), and the α-methylene-γ-lactone is trans-fused at C(6) and C(7) with H(6)β and H(7)α. Weak intermolecular hydrogen bonds exist between the hydroxy-group at C(2) and the lactone carbonyl [H ⋯ O 2.2(1), O ⋯ O 3.00(1)Å].