Nin-cyclohexyloxycarbonyl group as a new protecting group for tryptophan

Several new protecting groups were introduced at the Nⁱⁿ-position of tryptophan, and their reactivities were examined under the conditions used for peptide synthesis by Boc-strategy. Among them, the cyclohexyloxycarbonyl (Hoc) group was found to be the most suitable in terms of stability during elongation of the peptide chain and removability at the final HF reaction without resorting to the use of thiols.     

The methyl group as phosphate protecting group in nucleotide syntheses

A novel method is described for the removal of a methyl protecting group from phosphotriesters in oligonucleotides.     

二烷基磷酰基作为氨基保护基的研究

合成了N-烷基-N-磷酰基甘氨酸衍生物。在Lewis酸催化下成功地进行Freidel-Crafts反应,得到分子内环化产物苯并-3-氮杂环庚酮-[1]衍生物,并在温和条件下脱保护基。     

The t-butyl group as sensor group of the ortho effect

The ¹³C chemical shift difference between the Me group C atoms and the quaternary C atom of the t-Bu group in 58 p-, m- and o-substituted t-butyl-benzenes has been measured and analysed in terms of inductive. mesomeric and proximity effects. It is shown that the ortho effect is too complex to justify a unified explanation by a correlation treatment.     

Molecular torus group

Generally speaking, the highest symmetry of M?bius cyclacene molecule possesses the C₂ symmetry based on the theory of point group according to the previous works. However, based on the topology principle, the fundamental group of M?buis strip is an infinite continuous cyclic group and its border is made up of twice of the generator. Of course, the M?bius strip-like molecule is associated with a finite discrete cyclic symmetry group. For the cyclacene isomers constructed by several (n) benzene rings, these isomers include: the common cylinder Hückel cyclacene (HC-[n]) molecules, the M?bius cyclacene (MC-[n]) molecules by twisting the linear precursor one time (180°), and the multi-twisted M?bius strip-like cyclacene (M ^m C?[n]) molecules by twisting the linear precursor m times (m × 180°). The relevant results suggest that in addition to the point symmetry, there is a new kind of symmetry called the torus screw rotation (denoted as TSR). In this article, we take the M ^m C?[n] molecules as examples to discuss their TSR group and point group symmetry, and the relative symmetry adaptive atom sets as well as their atomic orbital (AO) sets. Here, the Cartesian coordinates is not quite fit for the investigation of these AOs, so it is replaced by either the torus orthogonal curvilinear coordinates (for M ^m C?[n] molecule) or the cylinder orthogonal curvilinear coordinates (for HC-[n] molecule). According to the features of cyclic group, the character table of the irreducible representation of the TSR group could be constructed easily. Some other relevant point-group symmetries maybe also belong to the molecule, so its symmetry maybe called as the torus group symmetry. For multi-twisted M?bius strip-like molecule, there are some correlations in topology characteristics.     

p-Anisyl group: A versatile protecting group for primary alcohols

A primary alcohol can be protected as a highly stable p-anisyl ether, which undergoes mild oxidative deprotection by ceric ammonium nitrate.     

Photoremovable NPEC group compatible with Ns protecting group in polyamine synthesis

Herein, we disclose an efficient combination of NPEC and Ns protecting groups in the synthesis of polyamine, by showing the orthogonal reactivity using N-NPEC-N-Ns alkylamines prepared from NPEC-NHNs. Selective photodeprotection of NPEC group in 12-mer polyamine and the complex conjugate has been further demonstrated toward the synthesis of novel polyamine natural product protoaculeine B.     

A one-pot conversion of the phenyldimethylsilyl group into a hydroxyl group

A phenyldimethylsilyl group attached to carbon can be converted into a hydroxyl group using either bromine or mercuric ion in an acetic acid solution of peracetic acid.     

Trityloxyethylamino group for the protection of phosphoryl group in oligonucleotide synthesis

Trityloxyethylamino group was used for the protection of 5′-phosphoryl group of deoxyribonucleoside. This group is not only protecting group of phosphate also the intermediate for the synthesis of d-ppA and d-pppA.     

The solubility of group I and group II fluorosulfates in fluorosulfuric acid

The solubilities at 25° of some Group I and Group II fluorosulfates in fluorosulfuric acid have been determined. The solubilities (g fluorosulfates/100 g fluorosulfuric acid) are LiSO₃F, 38.78; NaSO₃F, 80.21; KSO₃F, 63.83; RbSo₃F, 89.43; CsSO₃F, 132.4; MgSo₃F, 0.12; CaSO₃F, 16.39; SrSO₃F, 14.52 and BaSO₃F, 4.67.These results can be rationalized on the basis of lattice and solvation energy considerations. These solubility trends are consistent with those of the corresponding fluorides in hydrogen fluorides.