Donald L.D. Caspar (1927–2021)—pioneer of virus structures

Structural Chemistry - Donald L.D. Caspar (1927–2021) devoted his career to understanding the structure of viruses. He interacted with leading structural scientists of his time and...     

H. C. Brown Centennial (1912–2004)

Herbert Brown discovered the reaction of hydroboration and the most successful compound he made was sodium borohydride. His life and research activities took interesting turns and seemed often governed by serendipity. He was consistent in his hard work and dedication to chemistry. He was both an inorganic and an organic chemist and his research often presented challenges to the structural chemists.     

Gram scale synthesis of the C(1)–C(9) fragment of amphidinolide C

An allylic cis-epoxide prepared by Sharpless asymmetric epoxidation was transformed in nine steps and 41% overall yield to the cyclization precursor 4 via a key one carbon homologation. Cobalt-catalyzed aerobic oxidative cyclization of 4 gave the trans-THF in 94% yield at gram scale. Subsequent manipulations, including a Still–Gennari olefination, Sharpless asymmetric dihydroxylation, Corey–Fuchs alkynylation, and Kazmaier hydrostannylation provided the fully functionalized C(1)–C(9) fragment 2 suitable for cross-coupling. The sequence is readily scalable and provides gram quantities of 2.     

Pioneer of hyaluronan structural chemistry and other studies of polysaccharides: Torvard C. Laurent (1930–2009)

Torvard C. Laurent (1930–2009) was one of the pioneers of hyaluronan science and in particular of its structural aspects. He was the first who ever established the metrical characteristics of hyaluronan. He determined many of its physicochemical properties and their relationship to the versatile biological functions of this noted molecule. He also contributed to its medical applications. He was a leading personality in science administration and science policy in Sweden and internationally.     

Total synthesis of the ionophore antibiotic X-206. Studies relevant to the stereoselective synthesis of the C(17)–C(26) synthon.

A stereoselective synthesis of the keto-aidehyde 4, which embodies the structural features of the C(17)–C(26) section of the polyether X-206, is described.     

To the memory of Aleksandr Ivanovich Konovalov (1934–2021)

Russian Chemical Bulletin -     

Total synthesis of erythronolide B. 1. Skeleton assembly in (C9C13) + (C7C8) + (C1C6) sequence.

Erythronolide B has been synthesized starting from levoglucosan.     

Total synthesis of erythronolide B. 2. Skeleton assembly in (C5C9) + (C3C4) + (C1C2) + (C11C13) sequence.

Erythronolide B has been synthesized starting from levoglucosan.     

Regioselective copper(I)-catalyzed C–H hydroxylation/C–S coupling: expedient construction of 2-(styrylthio)phenols

Regioselective copper(I)-catalyzed C–H hydroxylation/C–S coupling of aryl thiols with vinyl halides was developed. Starting from substituted aryl thiols and vinyl halides, various 2-(styrylthio)phenol derivatives were efficiently prepared. The application of the synthetic methodology to generate the bioactive organic intermediate was also exemplified.     

FT/ICR–mass spectrometry in nanotechnology: the investigation of metalloid clusters

The particularity of metalloid clusters as a special kind of metal atom cluster is described. For the first time such metalloid clusters are investigated in the gas phase by means of FT/ICR–mass spectrometry, the results of which show that metalloid clusters represent a bridge between the bulk metal and metal compounds that can be found in solution after oxidation of the bulk metal. The metalloid clusters presented herein are [Ga₁₉R₆]^– (R=C(SiMe₃)₃), and SiAl₁₄Cp*₆ and the precursor Al₄Cp*₄ (Cp*= ⁵-C₅Me₅).     

Richard A. Lerner (1938–2021)—a structural biochemist and president of Scripps Institute

Structural Chemistry - Richard A. Lerner (1938-2021) was both a chemist and an MD. He investigated the structure of peptides and proteins, identified a sleep-inducing lipid, and is best known for...     

Iron-catalyzed alkenylation of cyclic ethers via decarboxylative sp(C)–sp(C) coupling

An efficient Fe(acac)₃-catalyzed decarboxylative C(sp²)–C(sp³) coupling reaction via oxidation of C–H bond adjacent to an oxygen atom has been developed successfully, in which cyclic ethers are selectively transformed into the corresponding alkenylation products with good chemical yields and excellent stereoselectivities. The mechanism was studied and the reaction was supposed to proceed through a radical oxidative coupling process.     

Microcalorimetric study of DNA–Cu(II)TOEPyP(4) porphyrin complex

The influence of new water soluble cationic metalloporphyrin Cu(II)TOEPyP(4) (meso-tetra-(4-N-oxyethylpyridyl)), analogue of Cu(II)TMPyP(4), on thermodynamic stability of DNA at various molar ratios of r = porphyrin/DNA b.p. (0 < r < 0.12) has been studied. It has been shown that Cu(II)TOEPyP(4) is a strong stabilizing agent for calf thymus DNA increasing its melting temperature from 75.5 to 99.5 °C, in the range 0 < r < 0.06. The melting enthalpy (∆H _m) does not change in the range 0.002 < r < 0.06 and it equals to 11.6 ± 0.8 cal/g. At r > 0.07, ∆H _m and T _m decrease, and at r = 0.12 they equal to 6.4 ± 0.6 cal/g and 92.5 °C, accordingly. We suggest that such centers of binding are the well documented 5′CG3′ sites and G-quadruplex at r < 0.01, and negatively charged phosphate groups at r > 0.01. On the basis of ∆H _m invariability with simultaneous increase of T _m in the range 0.002 < r < 0.06, it is shown that the DNA-Cu(II)TOEPyP(4) complex melting is not of an enthalpic nature but of an entropic one. The two-phase helix–coil transition of DNA at r < 0.01 is considered as a result of porphyrin redistribution in the melting process.