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ACD/Labs Blog

Arvin Moser
Logical reasoning and pattern recognition form the basis for making a pattern-to-fragment connection. For an unknown, the 1H NMR spectrum below shows 5 multiplets in the aromatic region. The multiplet at 7.57 ppm shows two overlapping multiplets: a broad signal overlapping a ‘doublet’ (noted as d*). Based on the multiplets’ tilt/lean and integrals, a 1,2-disubstituted...

Mikhail Elyashberg
Previously Wang et al reported three trace Lycopodium alkaloids, lycojaponicumins A and B with a 5/5/5/5/6 pentacyclic ring system and lycojaponicumin C with a 6/5/5/6 tetracyclic ring system. The same group later described the discovery of structurally unique alkaloid, Lycojaponicumin D (molecular formula was established to be C16H23NO3), with an unprecedented 5/7/6/6 tetracyclic skeleton formed by an unusual C3-C13 linkage.

Arvin Moser
An experienced elucidator can recognize spectral patterns and use this information to piece together a fragment. This puzzle examines one such pattern-to-fragment connection. A 1H NMR spectrum below shows the aromatic region for an unknown compound? Can you identify the fragment that would produce this pattern?

Mikhail Elyashberg
An aqueous extract of the roots of I. indigotica has been investigated by Chen and co-workers. In this work, the authors isolated and structurally characterized an indole alkaloid containing unusual dihydrothiopyran and 1,2,4-thiadiazole rings (molecular formula C18H17N3O2S2).

Arvin Moser
Quaternary carbons can be tricky in identifying. Keep your options open to ensure the bigger picture is not missed. The expanded region of the 13C NMR spectrum shows 4 signals for an unknown compound. The signal at 172 ppm represents 1 or 2 amide group(s). The higher intensity of the signal at 172 ppm in...

Mikhail Elyashberg
Liao et al isolated and elucidated the structure of a new natural product named as Asperjinone (molecular formula C22H20O6). Our analysis using ACD/Structure Elucidator resulted in the revision of the structure. The story of the structure revision is described in the Journal of Natural Products.

Arvin Moser
Spectral data is just data until you can see the bigger picture. This puzzle looks at a scenario of quaternary carbons. For an unknown compound, a standard 13C NMR spectrum (500 MHz CDCl3) was collected. The expanded region below shows 4 signals. Is the signal at 172 ppm attributed to 1 or 2 carbons (from...

Arvin Moser
Yes, basic counting is important in solving an unknown. How did you stack up with this puzzle? The 13C NMR spectrum below shows 7 signals in total, 3 intense signals and 4 weak signals. The 4 weak signals follow a quartet pattern produced by a CF3 group. The unknown contains a minimum of 4 C...

Mikhail Elyashberg
Ohlendorf and co-workers describe isolation and structure elucidation of Geranylphenazinediol (molecular formula C22H24N2O2), a phenazinediol substituted with an isoprenoid side chain. We used ACD/Structure Elucidator to elucidate structure of this new natural product using only its NMR spectroscopic data.

Arvin Moser
A key step in interpreting NMR data is in counting correctly the number of signals associated to the compound of interest. This puzzle covers one particular example. For a pure unknown compound, the 13C NMR spectrum below shows several 13C signals at varying intensities. What is the minimum C atom count?

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