Enantiomerically pure C -alkyl amides derived from cis and trans cycloalkane-1,2-dicarboxylic acids, respectively, have been synthesized and their behavior as organogelators has been investigated. These compounds include cis/trans diastereomeric cyclobutane and cyclohexane derivatives with the aim to explore the influence of the ring size as well as the relative configuration in their hierarchical self-assembly to form gels. High resolution H NMR spectroscopy studies allowed the determination of the dynamics of the gelation process in [D ]toluene and the sol-gel transition temperature. The morphology and size of the aggregates have been investigated and results have shown that, in the case of cyclobutane derivatives, the cis/trans stereochemistry is not relevant for the gelation behavior and the properties of the soft-materials obtained, but it is remarkable for cyclohexane diamides, which are better organogelators. The four compounds produce chiral aggregates despite that two of them are meso achiral molecules. We show herein that this fact is an example of stochastic symmetry breaking induced by sonication. The self-assembly of these molecules has been modelled providing information and support about the structure and the chirality of the aggregates.
The first example of a new protocol for the incorporation of γ-amino acids into peptides is reported. It involved a shikimic acid based stereoselective synthesis polyhydroxylated-2-nitromethylcyclohexanecarboxylic acids, which were directly incorporated into peptides.
New enantiomerically pure C16-alkyl diamides derived from trihydroxy cyclohexane-1,2-dicarboxylic acid have been synthesized from (−)-shikimic acid. The hydroxyl groups in these compounds are free or, alternatively, they present full or partial protection. Their gelling abilities towards several solvents have been tested and rationalized by means of the combined use of Hansen solubility parameters, scanning electron microscopy (SEM), and circular dichroism (CD), as well as computational calculations. All the results allowed us to account for the capability of each type of organogelator to interact with different solvents and for the main mode of aggregation. Thus, compounds with fully protected hydroxyl groups are good organogelators for methanol and ethanol. In contrast, a related compound bearing three free hydroxyl groups is insoluble in water and polar solvents including alcohols but it is able to gelate some low-polarity solvents. This last behavior can be justified by strong hydrogen bonding between molecules of organogelator, which competes advantageously with polar solvent interactions. As an intermediate case, an organogelator with two free hydroxyl groups presents an ambivalent ability to gelate both apolar and polar solvents by means of two aggregation patterns. These involve hydrogen bonding interactions of the unprotected hydroxyl groups in apolar solvents and intermolecular interactions between amide groups in polar ones.
Acetonide-3-trinervinone.-Title compound (I) is obtained during structure elucidation of diterpene trinervinol. Its molecular structure is established by X-ray diffraction study. -(SORIANO-GARCIA, M.; JIMENEZ, M.; GONZALEZ DE LA PARRA, M.; NAVARRO, A.; CAMPOS, M. P.; Acta Crystallogr., Sect. C: Cryst.
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This X-ray diffraction study establishes the molecular structure of the title compound, 2,2,4b ',8',8'-pentamethyl-6,10a'-epoxyspiro[ 1,3-dioxepane-5,2'-perhydrophenanthren]-7'-one, C23H3604, M. SORIANO-GARCIA et al. 1461 six-membered tings (A, B and C), and a five-and a seven-membered ring (D and E, respectively). The C ring is fused at C(8)---C(14)--C(13) to the D ring. The A/B, B/C and D/E rings are trans, trans and cis fused, respectively. The A, B and C tings adopt a distorted chair I C4 conformation. The D and E tings have envelope and half-chair 5H4 conformations, respectively. The crystal structure is stabilized by van der Waals interactions. There are two C--H..-O hydrogen bonds of less than 3.5 ~,. CommentGiven our interest in the phytochemical study of the Compositae family of plants found in Mexico, we have investigated the constituents of Piqueria trinervia, Cav (Jim6nez & Gonz~ilez de la Parra, 1983). A tetraol tricyclic diterpenoid, trinervinol, (1), was isolated from the flowers and leaves of this plant. During structure elucidation of (1) using chemical transformations and spectral data, compounds (2) and (3) were obtained.Trinervinol is a new diterpene with an isopimarane skeleton with a hydroxyl group at C(17). Details of the chemical transformations and spectral data of (2) and (3) are given by Jim6nez & Gonz~ilez de la Parra (1983). In this paper, the molecular structure of (3) ExperimentalCompound (3) was obtained during the elucidation of (1), which was isolated from the flowers and leaves of Piqueria trinervia, Cav. (10) 1.559 (5) C(11)~C (12) 1.548 (5) C(8)IC (14) 1.515 (5) C(13)----C (15) 1.536 (5) C(I 3)IC (17) 1.515 (5) C(4}----C (19) 1.538 (6) C(21 )---C (22) 1.512 (5) Crystal data C23H3604121.7 (4) C(3)----C(4)IC (18) 105.7 (3)117.7 (3) C(5)----C(6)----C (7) 109.9 (3) C(7)---C(8)----C (9) 112.6 (3) C(9)IC(8)--C (14) 109.1 (3) C (9) Geometric parameters (A, o)C(2)---C(3) 1.484 (6) C(4)-42 (5) 1.574 (5) C(6)--C (7) 1.521 (6) C(8)IC (9) 1.554 (5) C(5)IC (10) 1.568 (5) C(9)IC(I 1) t.545 (5) C(I 2)----C (13) 1.541 (5) C(I 3)----C (14) 1.522 (5) C(15)IC (16) 1.519 (6) C(4)---C(I 8)1.540 (6) C(10)---C (20) 1.558 (5) C(21)IC (23) 1.531 (5)108.3 (3) C(5)--C(10)IC (9) 106.6 (3) C(5)---C(10)----C (20) 112.4 (3) C(9)---C(11 )---C (I 2) 113.0 (3) C(12)IC(I 3)IC (14) 107.7 (3) C(14)---C(13)IC (I 5) 99.5 (3) C( 14)----C( 13)-42 (17) 116.5 (3)
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