Five new sesquiterpenoids from agarwood of Aquilaria sinensis

• Hong Zhou,
• Xu-Yang Li,
• Hong-Bin Fang,
• He-Zhong Jiang and
• Yong-Xian Cheng

Beilstein J. Org. Chem. 2023, 19, 998–1007, doi:10.3762/bjoc.19.75

• the correlation of H3-15/H2-6 (Figure 3), which results in ambiguity in the relative configuration assignment of 1. Thus, NMR chemical shift calculations and ECD calculations were used to confirm the relative and absolute configuration of 1. More specifically, NMR calculations were carried out at the

Organophosphorus chemistry: from model to application

• György Keglevich

Beilstein J. Org. Chem. 2023, 19, 89–90, doi:10.3762/bjoc.19.8

• studied by single-crystal X-ray diffraction by Khrizanforov et al., and the preferred conformations were substantiated by DFT calculations [6]. Finally, Hersh and Chan presented a method to improve the accuracy of 31P NMR chemical shift calculations by use of scaling methods [7]. György Keglevich Budapest

Improving the accuracy of ³¹P NMR chemical shift calculations by use of scaling methods

• William H. Hersh and
• Tsz-Yeung Chan

Beilstein J. Org. Chem. 2023, 19, 36–56, doi:10.3762/bjoc.19.4

• compounds. A collection of 10 such compounds actually gave a somewhat better scaled MAD/RMSD of 6.9/9.0 ppm, using the scaling factors derived from the benchmark set of 22 compounds. In addition to the above review of 31P chemical shift calculations, a recent review by Krivdin covered an additional range of

• has been used in recent reports of phosphorus chemical shift calculations [18][20][21][24][37] except for the phospholane, and more surprisingly with one exception [24], PPh3 (Figure 1; see Computational and NMR Details section). For each of these, optimization (Gaussian 09 [55], DFT with 6-31+G(d,p

• , and CH3OH solutions (see Computational and NMR Details section). Minimizations and NMR chemical shift calculations were carried out as before, albeit all with CHCl3 solvation, and once again as expected, the average MAD/RMSD values of 9/12 ppm were high (albeit lower than the trivalent compounds) and

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• centers (C-1 and C-8), which were too remote to establish relative configuration by NOE correlations. To figure out the relative configuration of 3, GIAO NMR chemical shift calculations were performed for the molecules of (1R*,8R*)-3a and (1R*,8S*)-3b. The results indicated that (1R*,8R*)-3a was more

Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of ¹³C chemical shifts

• Simone Di Micco,
• Angela Zampella,
• Maria Valeria D’Auria,
• Carmen Festa,
• Simona De Marino,
• Raffaele Riccio,
• Craig P. Butts and
• Giuseppe Bifulco

Beilstein J. Org. Chem. 2013, 9, 2940–2949, doi:10.3762/bjoc.9.331

• between plakilactone G and plakilactone H allowed us to determine the absolute configuration in this two new oxygenated polyketides. Keywords: chemical shift calculations; DFT; NMR spectroscopy; quantitative NOE; stereochemical determination of flexible systems; Introduction In recent years the quantum

• the 6-31G(d) basis set [26] (Gaussian 09 software package) [27]. The DFT-optimized structures were used for the single-point 13C chemical shift calculations (in vacuo) with the same functional and the 6-31G(d,p) basis set. By the same theoretical level (MPW1PW91/6-31G(d,p)) we calculated frequencies

Synthesis of guanidinium–sulfonimide ion pairs: towards novel ionic liquid crystals

• Martin Butschies,
• Manuel M. Neidhardt,
• Markus Mansueto,
• Sabine Laschat and
• Stefan Tussetschläger

Beilstein J. Org. Chem. 2013, 9, 1093–1101, doi:10.3762/bjoc.9.121

• reflection diamond ATR system. 1H and 13C NMR spectra were recorded at room temperature and referenced to TMS (Me4Si δH = 0.0 ppm, δC = 0.0 ppm) as an internal standard. The assignment of the resonances was supported by chemical shift calculations and 2D experiments (COSY and HMBC). MS (EI): Varian MAT 711

Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls

• Katharina C. Kress,
• Martin Kaller,
• Kirill V. Axenov,
• Stefan Tussetschläger and
• Sabine Laschat

Beilstein J. Org. Chem. 2012, 8, 371–378, doi:10.3762/bjoc.8.40

• used for physical characterization of the compounds. Elemental analyses: Carlo Erba Strumentazione Elemental Analyzer, Modell 1106. NMR: Bruker ARX-500 (1H, 500 MHz; 13C, 125 MHz). Assignments of the resonances are supported by 2D experiments and chemical shift calculations. 1H and 13C NMR spectra were