A new probabilistic approach is introduced for the determination of the absolute structure of a compound which is known to be enantiopure based on Bijvoet-pair intensity differences. The new method provides relative probabilities for different models of the chiral composition of the structure. The outcome of this type of analysis can also be cast in the form of a new value, along with associated standard uncertainty, that resembles the value of the well known Flack x parameter. The standard uncertainty we obtain is often about half of the standard uncertainty in the value of the Flack x parameter. The proposed formalism is suited in particular to absolute configuration determination from diffraction data of biologically active (pharmaceutical) compounds where the strongest resonant scattering signal often comes from oxygen. It is shown that a reliable absolute configuration assignment in such cases can be made on the basis of Cu K data, and in some cases even with carefully measured Mo K data.

The previously described method for absolute structure determination [Hooft, Straver & Spek (2008). J. Appl. Cryst.41, 96–103] assumes a Gaussian error distribution. The method is now extended to make it robust against poor data with large systematic errors with the introduction of the Student t‐distribution. It is shown that this modification makes very little difference for good data but dramatically improves results for data with a non‐Gaussian error distribution.

A s y m m e t r i c O r g a n o c a t a l y t i c S y n t h e s i s o f c i s -S u b s t i t u t e d D i h y d r o b e n z o f u r a n o l sAbstract: The diastereo-and enantioselective synthesis of 3-hydroxy 2,3-dihydrobenzofurans via an intramolecular cis-selective aldol reaction employing proline-type organocatalysts is described enabling a new entry to coumarine natural products.

A single crystal of C60 grown from a toluene solution has been studied by X-ray diffraction at room temperature. The lattice is face-centered cubic, with space group Fm~m and Z = 4, which agrees with previous powder diffraction measurements. It is shown that, contrary to what is obtained in other plastic crystals, the Pauling-Fowler model (the so-called free rotation one), wfiich implies an isotropic molecular disorder, gives a better description of the molecular packing than the site model does. It is concluded that the molecules undergo a rotational diffusion as previous molecular dynamics simulations have described.

From hydrothermal synthesis needle-shaped crystals of [Ca 3 (C 6 H 5 O 7 ) 2 (H 2 O) 2 ]·2H 2 O were obtained. The crystal structure was determined by single-crystal X-ray experiments and confirmed by powder data (P1 (no. 2) a = 5.9466(4), b = 10.2247(8), c = 16.6496(13) Å, α = 72.213(7)°, β = 79.718(7)°, γ = 89.791(6)°, V = 947.06(13) Å 3 , Z = 2, R1 = 0.0426, wR2 = 0.1037). The structure was