Three new sesquiterpene alkaloids of the polyveoline type containing eight‐membered lactam rings named greenwaylactam A (1), B (2) and C (3) were isolated from the leaves of a Cameroonian medicinal plant Greenwayodendron oliveri (Engl.) Verdc along with three known compounds diacetylpolyveoline (4), N‐acetyl‐8α‐polyveolinone (5) and methyl pheophorbide‐A (6). These comprise the first members of a new class of ξ‐lactam sesquiterpenes. Compounds were isolated by means of successive column chromatographies and their structures were elucidated by extensive NMR spectroscopic analyses and HRESIMS. The configuration of 1 was deduced from its single‐crystal X‐ray diffraction. The crude extract and some isolated compounds were assessed for their antibacterial activity against four enteric bacterial strains Escherichia coli, Salmonelles typhi, Shigella dysenterie and Klebseilla pneumonie using the micro‐dilution method. Compounds 1, 2, 5 and 6 were the most active with MIC values varying between 31.25–250 μg/mL.

A new organic-inorganic hybrid salt pipéridinium trans-diaquabis(oxalato)chromate(III) tetrahydrate, (C 5 H 10 NH 2 )[Cr(C 2 O 4 ) 2 (H 2 O) 2 ]•4H 2 O (1), has been synthesized in water and characterized by FTIR and UV-Vis spectroscopies, elemental and thermal analyses and by single-crystal X-ray diffraction. 1 crystallizes in the orthorhombic non-centrosymmetric space group Cmc2 1 with the unit cell parameters a = 7.4329(3), b = 9.9356(5), c = 23.6756(11) Å, α = β = γ = 90˚, V = 1748.45(14) Å 3 and Z = 4. The structure of 1 consists of [Cr(C 2 O 4 ) 2 (H 2 O) 2 ] − mononuclear anions, piperidinium cations and uncoordinated water molecules. The Cr III ion in the complex [Cr(C 2 O 4 ) 2 (H 2 O) 2 ] − is coordinated in a slightly distorted octahedral environment by four O atoms from two chelating oxalate dianions in the equatorial plane, and two O atoms from trans-coordinated water molecules occupying the apical positions. In the crystal, N-H⋯O and O-H⋯O hydrogen bond interactions connect the components into a 3-D framework. The IR spectrum of 1 is consistent with the presence of the various molecular building constituents, namely oxalato and aqua ligands, piperidinium cations and solvent water molecules. The UV-Vis spectrum shows two absorption bands around 564 and 416 nm which are

The crystal structure of the title compound, C32H39NO4, confirms the absolute configuration of the seven chiral centres in the mol­ecule. The molecule has a 1,1-dimethylprop-2-enyl substituent on the indole nucleus and this nucleus shares one edge with the five-membered ring which is, in turn, connected to a sequence of three edge-shared fused rings. The skeleton is completed by the 7,7-trimethyl-6,8-dioxabi­cyclo­[3.2.1]oct-3-en-2-one group connected to the terminal cyclohexene ring. The two cyclohexane rings adopt chair and half-chair conformations, while in the dioxabi­cyclo­[3.2.1]oct-3-en-2-one unit, the six-membered ring has a half-chair conformation. The indole system of the mol­ecule exhibits a tilt of 2.02 (1)° between its two rings. In the crystal, O—H⋯O hydrogen bonds connect mol­ecules into chains along [010]. Weak N—H⋯π inter­actions connect these chains, forming sheets parallel to (10-1).

A novel organic-inorganic chromium(III) hybrid salt, triethylammonium trans-diaquabis(oxalato-κ 2 O 1 ,O 2)chromate(III), (C 6 H 16 N)[Cr(C 2 O 4) 2 (H 2 O) 2 ] (1), has been synthesized in aqueous solution and characterized by elemental and thermal analyses, FTIR and UV-Vis spectroscopies, and by single crystal X-ray structure determination. Compound 1 crystallizes in the orthorhombic system, Pbcn space group with the unit cell parameters a = 11.1776(10), b = 7.6105(10), c = 17.5654(2) Å, α = β = γ = 90˚, V = 1494.24(3) Å 3 , Z = 4 and Z' = 1/2. The structure of 1 consists of [Cr(C 2 O 4) 2 (H 2 O) 2 ] − mononuclear anions and triethylammonium [(C 2 H 5) 3 NH] + cations. In the anionic unit, the Cr III ion is six coordinated, in a distorted octahedral geometry, by four equatorial O atoms of two oxalate anions acting as chelating ligands and two O atoms from trans-coordinated water molecules occupying the apical positions with longer metal-oxygen distances. In the solid, O-H … O and N-H … O intra and inter molecular hydrogen bonding interactions connect the components into a 3D network. The triethylammonium cations are disordered among two possible orientations with occupancies rates around 50% for C4, N1, C1a, C1b, C4 ii , N1 ii , C1a ii , C1b ii

The subsoil of most developing countries, particularly African countries, contain a great variety of minerals and ores. Nowadays, mining activities are extensively performed. In the meantime, it is noticed that the teaching of crystallography and its applications remains undeveloped in most universities, in sub-Saharan african countries in particular. In this communication, the authors will attempt to propose teaching methods and techniques which could lead to a wider dissemination of crystallography, based on their own experience as teachers of this subject in their country of origin.