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organic compounds
The crystal structures of two dolabrane diterpenes, ent-2-seco-3-nor-5α,4,15-dioxo-16-hydroxydolabran-2-oic acid, C19H30O5, (I), and ent-2-seco-3-nor-5α,16-chloro-15-hydroxydolabran-2-oic acid, C19H31ClO4, (II), have been determined at room temperature. They revealed the presence of two trans-fused rings having a chair conformation and they confirmed previous NMR studies showing that the C9 substituent is trans with respect to those at C8 and C10. Furthermore, we observed that the longer Csp3—Csp3 distances occor for C9—C10 and C5—C10, which is in agreement with the values found in other diterpenes. These are the first reported crystal structures of dolabrane molecules.