Neutron diffraction study of the crystal and magnetic structure of the ionic ferromagnet Cs2CrCl4

Neutron powder diffraction has been used to investigate the crystal and magnetic structure of the ionic ferromagnet Cs₂CrCl₄, T_c ～ 58K. Data taken at ambient temperature, 78 and 4.2K indicate the structure remains tetragonal $\text{I4}\text{mmm}$ at low temperatures. A ferromagnetic alignment of the spins is confirmed. The ordered moment at 4.2K is found to be 4.1 ± 0.2μ_B, and the best agreement between the calculated profile and the data suggests its direction lies at an angle of 56 ± 6° to the unique axis.     

The occurrence of prostaglandins PGE2 and PGF2α in a plant - the red alga Gracilaria Lichenoides.

Prostaglandins PGE₂ and PGF_2α were isolated from the aqueous extract of the red alga $\text{Gracilaria lichenoides}$, after an investigation of the extract's anti-hypertensive properties.     

Isolation and synthesis of 1-methylisoguanosine,a potent pharmacologically active constituent from the marine sponge tenadiadigitata

A new pharmacologically active agent isolated from the marine sponge $\text{Tedania}$$\text{digitata}$ has been identified as 1-methylisoguanosine ($\text{1}$) by spectral and degradative chemical methods and synthesis from a β-D-ribofuranosylimidazole ($\text{2}$).     

A Very Short Uranium(IV)–Rhodium(I) Bond with Net Double‐Dative Bonding Character

Reaction of [U{C(SiMe₃)(PPh₂)}(BIPM)(μ‐Cl)Li(TMEDA)(μ‐TMEDA)_0.5]₂ (BIPM=C(PPh₂NSiMe₃)₂; TMEDA=Me₂NCH₂CH₂NMe₂) with [Rh(μ‐Cl)(COD)]₂ (COD=cyclooctadiene) affords the heterotrimetallic U^IV?Rh^I₂ complex [U(Cl)₂{C(PPh₂NSiMe₃)(PPh[C₆H₄]NSiMe₃)}{Rh(COD)}{Rh(CH(SiMe₃)(PPh₂)}]. This complex has a very short uranium–rhodium distance, the shortest uranium–rhodium bond on record and the shortest actinide–transition metal bond in terms of formal shortness ratio. Quantum‐chemical calculations reveal a remarkable Rh U^IV net double dative bond interaction, involving Rh^I 4d ‐ and 4d_xy/xz‐type donation into vacant U^IV 5f orbitals, resulting in a Wiberg/Nalewajski–Mrozek U?Rh bond order of 1.30/1.44, respectively. Despite being, formally, purely dative, the uranium–rhodium bonding interaction is the most substantial actinide–metal multiple bond yet prepared under conventional experimental conditions, as confirmed by structural, magnetic, and computational analyses.     

Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi)

The synthesis and characterisation is presented of the compounds [An(Tren^DMBS){Pn(SiMe₃)₂}] and [An(Tren^TIPS){Pn(SiMe₃)₂}] [Tren^DMBS=N(CH₂CH₂NSiMe₂Bu^t)₃, An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃, An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U?Sb and Th?Sb moieties are unprecedented examples of any kind of An?Sb molecular bond, and the U?Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th?Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U?Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An?An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U?Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route.     

Book Review: Self-Stabilization,by Shlomi Dolev. Cambridge,MA: The MIT Press,Cambridge MA, 2000. 197 pp. ISBN 0-262-04178-2

Nonlinear Dynamics, Psychology, and Life Sciences -     

An optimised synthesis of SG3376, a non-cleavable antibody-drug conjugate pyrrolobenzodiazepine drug-linker

In recent years, antibody-drug conjugates (ADCs) have been evaluated in a growing number of clinical trials. Preclinical evaluation and the synthetic accessibility of cleavable pyrrolobenzodiazepine drug-linkers, such as talirine and tesirine, have been previously described. This article details how the synthesis of SG3376, a non-cleavable pyrrolobenzodiazepine drug-linker, has been optimised to provide access to late-stage versatile intermediates in a robust and scalable fashion. Of particular importance was the selective deprotection of primary N-Boc in the presence of secondary N-Boc and secondary O-TBS. SG3376 was conjugated to trastuzumab and the resulting ADC was found to have potent cytotoxic activity in a number of HER2-positive cancer cell lines.