The γ‐form of n‐eicosanol

In the crystal of the title compound, C₂₀H₄₂O, the mol­ecules are packed in layers parallel to the (100) plane. The alkyl chains are parallel to the [30] direction and these molecular chains are hydrogen‐bonded into chains parallel to the c axis. All C—C bonds of the alkyl chain show an antiperiplanar (trans) conformation, with a slight deviation from the ideal value (180°) in the C—C bonds close to the hydrogen bonds. The length of the alkyl chain is 27.92 (2) Å and the tilt angle is 59.7 (2)°.     

α‐Onocerin chloro­form hemisolvate

The triterpenoid natural product α‐onocerin [8,14‐secogammacera‐8(26),14(27)‐diene‐3,21‐diol], determined here as the chloro­form hemisolvate, C₃₀H₅₀O₂·0.5CHCl₃, consists of two independent symmetric trans‐decalin C₁₅ building blocks. Hydro­gen bonds between the hydroxyl groups form an infinite two‐dimensional network perpendicular to the c axis.     

Two N‐ortho‐nitro­benzene­sulfonyl α,α‐disubstituted amino acid adducts

The carboxy group of 2‐methyl‐N‐[(2‐nitrophenyl)sulfonyl]­alanine, C₁₀H₁₂N₂O₆S, forms centrosymmetric hydrogen‐bonded dimers with an O?O distance of 2.629 (2) Å and an intramolecular N—H?O(nitro) hydrogen bond N?O distance of 2.823 (2) Å. 1‐[(2‐Nitro­phenyl)­sulfonyl­amino]­cyclo­hexane­carboxyl­ic acid, C₁₃H₁₆N₂O₆S, has Z′ = 2 and forms similar interactions.     

A kinetic study of the atmospheric photolysis of α‐dicarbonyls

Photolysis frequencies of biacetyl, methyl glyoxal, and glyoxal have been determined relative to the photolysis frequency of NO₂. The values were measured under natural sunlight conditions in a large‐volume outdoor reaction chamber. The experimental results obtained are compared to photolysis frequencies used in current models of tropospheric photo‐oxidant formation. For biacetyl, a ratio of J(biacetyl)/J(NO₂) = (0.0364 ± 0.0026) was found, in good agreement with previous measurements and models. For methyl glyoxal, however, the experimental photolysis frequency ratios were significantly larger than those calculated from models. This could only partly be explained by reaction of methyl glyoxal with HO₂. Due to this inconsistency, it is preferred not to cite a ratio for J(methyl glyoxal)/J(NO₂). The agreement between calculated and experimental photolysis frequency ratios of glyoxal was reasonably good, a ratio of J(glyoxal)/J(NO₂) = 0.0109 has been found, with estimated overall error margins of about 30%. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 9–20, 2001     

Iodine(III)‐Catalyzed Rearrangements of Imides: A Versatile Route to α,α‐Dialkylated α‐Hydroxy Carboxylamides

A tertiary hydroxy group α to a carboxyl moiety comprises a key structural motif in many bioactive substances. With the herein presented metal‐free rearrangement of imides triggered by hypervalent λ³‐iodane, an easy and selective way to gain access to such a compound class, namely α,α‐disubstituted‐α‐hydroxy carboxylamides, was established. Their additional methylene bromide side chain constitutes a useful handle for rapid diversification, as demonstrated by a series of further functionalizations. Moreover, the in situ formation of an iodine(III) species under the reaction conditions was proven. Our findings clearly corroborate that hypervalent λ³‐benziodoxolones are involved in these organocatalytic reactions.     

A Novel Synthesis of γ,δ‐Unsaturated Aldehydes from α‐Formyl‐γ‐lactones

A preparatively useful one‐step transformation of γ,γ‐disubstituted α‐formyl‐γ‐lactones into trisubstituted γ,δ‐unsaturated aldehydes is described, by means of catalytic amounts of either AcOH or AcOEt in the vapor phase over a glass support. A mechanistic rationale is proposed.     

The Renaissance of α‐Methylene‐γ‐butyrolactones: New Synthetic Approaches

The amount of research activity concerning α‐methylene‐γ‐butyrolactones and α‐alkylidene‐γ‐butyrolactones has increased dramatically in recent years. This Review summarizes the structural types, biological activities, and biosynthesis of these compounds, concentrating on publications from the past 10 years. Traditional approaches to α‐methylene‐γ‐butyrolactones and α‐alkylidene‐γ‐butyrolactones are then reviewed together with novel approaches, including those from our own research group, reported more recently.     

From α‐carbamoyl‐α‐cyano­oxiranes to 3‐halogenopyruv­amides

The crystal structures of the first stable α‐diol from the α‐halogenopyruv­amide series, 3‐chloro‐2,2‐di­hydroxy‐3‐phenyl­propan­amide, C₉H₁₀­ClNO₃, and three products [3‐(4‐chloro­phenyl)‐2‐cyano‐2,3‐epoxy­propan­amide, C₁₀H₇­ClN₂O₂, 3‐bromo‐2‐cyano‐2‐hydroxy‐3‐p‐tolyl­propan­amide, C₁₁H₁₁Br­N₂O₂, 3‐bromo‐2‐oxo‐3‐p‐tolyl­propan­amide, C₁₀H₁₀­BrNO₂] obtained during the systematic synthesis of α‐halogenopyruv­amides are reported. The crystal structures are dominated by hydrogen bonds involving an amide group. The stability of the geminal diol could be ascribed to hydrogen bonds which involve both hydroxyl groups.     

Two polymorphs of chlorpropamide: the δ‐form and the high‐temperature ɛ‐form

The ɛ‐form of chlorpropamide [systematic name: 4‐chloro‐N‐(propylaminocarbonyl)benzenesulfonamide], C₁₀H₁₃ClN₂O₃S, has been obtained as single crystals from solution (and not as a polycrystalline sample by heating the α‐, γ‐ or δ‐forms). The results of anisotropic structure refinements for the ɛ‐ and δ‐forms are reported. The density of the δ‐polymorph is the highest, and that of the ɛ‐polymorph the lowest, among the five known chlorpropamide polymorphs. The main intermolecular hydrogen‐bonding pattern in polymorphs δ and ɛ is the same as in polymorphs α, β and γ, but the conformations differ. The densities of the polymorphs were found to depend on the molecular conformations.