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The syntheses of new o-carboranyldiols bearing aromatic rings bis-[R(hydroxy)methyl]-1,2-dicarba-closo-dodecaborane (R = 2-pyridyl 1a, 3-pyridyl 1b, 4pyridyl 1c, 2-quinolyl 1d, 4-quinolyl 1e, phenyl 1f) are reported. The compounds are obtained as mixtures of meso (syn) and racemic (anti) stereoisomers with a slight diastereomeric excess (syn:anti ratio of 0.7:1) in all cases but in 1b. The crystal structures of the meso compounds syn-1a•2MeOH, syn-1b, syn-1f•0.25H 2 O and racemic anti-1a•MeOH, anti-1a•EtOH, and anti-1d•2H 2 O are reported. We provide an analysis of these compounds by means of NMR and X-ray crystallography, in the context of crystal engineering and chiral recognition. The results show that the crystal packings for these alcohols are dominated by the supramolecular O−H•••N and/or O− H•••O hydrogen bonds. Supramolecular analysis of all compounds in this work reveals that homochiral self-assembly, that is, formation of homochiral hydrogen bonded complexes, prevails over heterochiral self-assembly (formation of heterochiral hydrogen bonded complexes).

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A estrutura molecular predominante para o DL e para o D-gliceraldeído foi estudada utilizando espectroscopia de infravermelho e de ressonância magnética nuclear. As duas técnicas mostraram que, a temperatura ambiente, estes compostos apresentam apenas uma pequena porcentagem da forma aldeído. Estes estudos mostraram que a forma aldeído para o D-(+)-gliceraldeido coexiste, como componente em pequena proporção, com uma mistura complexa de diastereosômeros do 2,5-di-hidroxi-3,6-di-hidroximetil-1,4-dioxano, enquanto a mistura racêmica é constituída por dois compostos principais. A estabilidade dos diasteroisômeros é controlada pela formação de ligações de hidrogênio intramoleculares em decorrência do efeito anomérico, que define a posição favorável para o grupo hidroxila. As interações anoméricas endo e exo são originadas pela interação estereoeletrônica n O → σ* C-O . Utilizando cálculos teóricos em nível B3LYP/6-31G(d,p) foi possível estabelecer a estrutura dos confôrmeros favorecidos.The predominant molecular structure of DL and D-glyceraldehyde has been studied with infrared and nuclear magnetic resonance spectroscopies. Both techniques show that these compounds at room temperature have a minor percentage of the aldehydic form. These studies showed that D-(+)-glyceraldehyde coexists in a minor proportion as a component of a complex mixture of diasteroisomers of the 2,5-dihydroxy-3,6-dihydroxymethyl-1,4-dioxane, while the racemic mixture is made of two main compounds. The stability of the isolated diasteroisomers is controlled by the formation of intramolecular hydrogen bonds that are formed under the control of the anomeric effect which defines the favored position for the hydroxyl group. The endo and exo-anomeric interactions have their origin in the stereoelectronic interaction n O → σ* C-O . Using theoretical calculations at B3LYP/ 6-31G(d,p) level, it was possible to establish the structure of the favored conformers.Keywords: DL-glyceraldehyde, D-glyceraldehyde, 1,4-dioxanes, nuclear magnetic resonance, density functional calculations, stereoelectronic effects, anomeric effect, hydrogen bond, weak interactions IntroductionThe so-called weak interactions are fundamental in the development of emerging areas of Chemistry such as Supramolecular Chemistry and Crystal Engineering. These interactions are also of great importance in the molecular recognition that controls biological functions, so it is paramount to understand their origin, establish their magnitude and the factors that modify them. In this study, we selected for the analysis glyceraldehyde, a molecule where several types of these interactions coexist and affect molecular energy.D-glyceraldehyde is without any doubt one of the most important compounds in the fields of chemistry, biochemistry and biology. It is the first carbohydrate produced by most plants in photosynthesis as 3-phosphoglycerate. 1 Most chemists and biochemists are familiar with the D-and L-molecular structures of glyceraldehydes which appear in Chemistry and 468 García-Jiménez et al...

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