The crystal and molecular structure of a p-bromobenzoyl derivative of ε-caesalpin

Abstract

The crystal structure of a p-bromobenzoyl derivative, C27H3306Br, of the diterpene e-caesalpin has been determined by the heavy-atom method using three-dimensional X-ray data. The absolute configuration was established from the anomalous scattering of the bromine atom. The three six-membered rings A, B and C are fused to form a trans-anti-trans system. Rings A and B both occur in the chair form while the unsaturated ring C adopts a distorted half-chair conformation. An intramolecular hydrogen bond (2.649/~) occurs between the two 1,3-diaxial hydroxyl groups. The crystals are monoclinic, space group P21 with two molecules in a unit cell of dimensions a = 6.563, b = 12.999, c = 14.809/~; B=94.50 °. The structure has been refined by least-squares methods to a final residual (R) of 12.3% for 3115 reflexions.

ChemInform Abstract: Caesaljaponins A and B: New Cassane‐Type Furanoditerpenoids from the Seeds of Caesalpinia decapetala var. japonica

“…The IR and UV spectra of 2 were similar to those of 1. The NMR data of 2 were almost the same as those of 1 except for the chemical shifts of C(7), C(8), C(9), C(11), C (14), and C (17). The HMBCs of 2 shown in Fig.…”

“…The connectivity between C(3) and C(5) through C (4) was established based on the HMBC from a tertiary Me group (Me(19)) to C(3), C(4), and C (5). The connectivity between the remaining partial structures was deduced by analysis of the HMBCs from the other tertiary Me group (Me (17)) to C(8), C (13), and C (14), from OÀCH 2 (20) to C(1), C(5), C (9), and C(10), from CH 2 (11) to C(12) and C (13), from HÀC (15) to C (12) and C (13), and from HÀC (16) to C(12) and C(13), to construct the cassane-type furanoditerpene skeleton in 1 (Fig. 1).…”

The crystal structure of DL-4β,10β-dimethyl-6-ethylamino-4-hydroxycarbonyl-2,3,5β,10-tetrahydrophenanthr-1-one lactam, C19H21O2N

“…This form is preferred since the 1,3 diaxial interaction [C(18)... C(19)] which would be present in a chair is relieved. The C(18)... C(19) non-bonded distance is 3.604(2)/k while in a chair the 1,3 diaxial methyl-methyl distances are usually observed in the range 3.0-3"3 A (Birnbaum & Ferguson, 1969). The shortest hydrogen-hydrogen contact, H(I82)... H(192), of 2.433(27)~ is equal to the van der Waals distance of 2.4 ,It (Pauling, 1960) and indicates the absence of strain.…”

“…However, these bond lengths are all between highly substituted carbon atoms and lengthening of such bonds is common. For instance, in a derivative of e-caesalpin two C-C single bonds were observed as 1.603(17) and 1.591(17)A (Birnbaum & Ferguson, 1969), and in naphthalene C-C bond lengths up to 1.422(4) A were observed (Almenningen, Bastiansen & Dyvik, 1961).…”

The crystal structure of dendrocrepine hydrobromide

“…Table 6. Intramolecular bond angles (o), been previously observed (Birnbaum & Ferguson, 1969). There are six C-N ÷ bonds in the molecule, each protonated nitrogen atom being attached to three C(sp 3) atoms, and the mean of their lengths is 1.502 .~, normal for this kind of bond (Singh & Ahmed, 1969).…”