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ACD/Labs Blog

Mikhail Elyashberg
M. Cao and co-workers described the isolation and structure elucidation of 10 new alkaloids belonging to the Daphniphyllum alkaloids family. The spectral data presented for one of the compounds, Daphmacromine A (molecular formula C25H37NO5), were used to challenge ACD/Structure Elucidator.

Arvin Moser
The nomenclature rules for organic compounds set by the International Union of Pure and Applied Chemistry (IUPAC) committee (http://www.iupac.org/) do offer flexibility in some areas especially in cases where old publications have old terms. Below are some examples. The answers for the structures, as based on the IUPAC nomenclature rules, are listed below. Some links...

Arvin Moser
Following a successful attempt at solving an unknown, the next step may be to determine a name for the novel compound. The nomenclature rules for organic compounds are set in place by the International Union of Pure and Applied Chemistry (IUPAC) committee (http://www.iupac.org/). For the following compounds, which names adhere to the IUPAC nomenclature rules?

Arvin Moser
Given any experimental data, producing a list of scenarios that are consistent with the data can help guide an elucidator through the problem while ensuring nothing gets overlooked. For an unknown compound, the carbon count is identified at 18 in total. The 13C NMR spectrum below indicates 19 carbon atoms. There are two 13C signals,...

Arvin Moser
To identify co-eluting components on a chromatogram, one searches for any distinct differences between the components. There are basically three criteria to check the XICs (extracted ion chromatograms) for to confirm whether the m/z signals pertain to the same component: line shape, signal apex and retention time range. The XICs for m/z 188.1 and 205.1...

Arvin Moser
Sorting out what compounds are present in a mixture is a difficult task. The process is further complicated when the compounds co-elute on a chromatographic run. An LC/MS (ESI+) was collected for an unknown sample comprising of small organic molecules. The total ion chromatogram (TIC shown in black) shows a signal at 2.86 minutes. The...

Arvin Moser
Coupling patterns that overlap can be deceptively simple. There are two possible coupling patterns for the CH2 signal at 3.39 ppm (top spectrum): a singlet or two ‘doublets’ (AB spin system) tilted towards each other. The bottom spectrum shows an example of two ‘doublets’ where the outer signals at 3.34 and 3.43 ppm are barely...

Arvin Moser
Coupling patterns can be deceptively simple. For an unknown compound, the expanded region of a 1H NMR spectrum below shows a signal at 3.39 ppm for a CH2 group. Is the coupling pattern for this two spin system a ‘true’ first-order singlet?

Mikhail Elyashberg
Wang et al isolated a novel alkaloid lycojaponicumin (molecular formula C16H21NO4) from the alkaloidal extract in a trace amount, with a unique 5/5/5/5/6 pentacyclic ring system including two fused tetrahydroisoxazole rings. The structure was elucidated by spectroscopic methods and X-ray diffraction analysis.

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