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ACD/Labs Blog

Mikhail Elyashberg
This month we re-visit the example of structure revision of Epohelmin A with structure revision utilizing ACD/Structure Elucidator Suite, which demonstrates how the software allows a researcher to avoid complex multi-stage synthesis to refute a wrong proposed structure and prove the revised one.

Arvin Moser
A key step in being a successful elucidator is to understand the principles behind the experiment. Below is one such case. For the following known compound, the 1H -13C HSQC-DEPT (or multiplicity-edited HSQC) spectrum (collected at 150 Hz coupling constant) below shows a negative correlation (blue) at 2.72 and 61.1 ppm with a 1H integral...

Mikhail Elyashberg
To understand the molecular mechanism underlying the genus-specificity of ascidians' sperm chemotaxis, Matsumori et al investigated the structure of a novel compound Ascidia-SAAF 2 (molecular formula C27H44O10S2Na2), which was isolated from the eggs of the ascidian Ascidia sydneiensis. Utilizing Structure Elucidator Suite allowed the correct structure of unknown, and its configuration upon a double bond to be determined.

Mikhail Elyashberg
Kim et al isolated and identified two unprecedented phosphorus-containing iodinated polyacetylenes, Phosphoiodyn A and B, from a Korean marine sponge Placospongia sp. Here we will describe the structural elucidation of Phosphoiodyn A (molecular formula C16H24O4PI).

Arvin Moser
An HMBC experiment correlates atoms over a longer range from 2-4 bonds. However, it can also exhibit correlations for 1-bond separation. For a pure, unknown compound, the 1H -13C HMBC spectrum below shows three correlations to the carbon at 42 ppm. The correlations at 3.50 and 4.05 ppm correlate the 1H signal at 3.75 ppm...

Mikhail Elyashberg
Aquatolide is a humulane-derived sesquiterpenoid lactone isolated from Asteriscus aquaticus. The structure originally proposed on the basis of 1D and 2D NMR analysis contains an exceedingly rare ladderane substructure. As a result of the quantum-chemical (QM) calculations of the 13C and 1H chemical shifts and associated coupling constants for a series of possible structures, it was shown that the proposed structure was incorrect. We applied a well-established Computer Assisted Structure Elucidation (CASE) method to the problem, in order to compare results with the QM method.

Arvin Moser
An HMBC experiment can be a key part in solving for an unknown compound. In this puzzle, ‘extra’ correlations add an extra degree of difficulty to its interpretation. For a pure, unknown compound, the 1H -13C HMBC spectrum below shows three correlations to the carbon at 42 ppm. Can you interpret how the correlations at...

Mikhail Elyashberg
Wang and co-workers isolated Jatrophalactam (molecular formula C20H29NO3), a novel diterpenoid lactam possessing an unprecedented skeleton from the roots of Jatropha curcas.

Arvin Moser
13C-13C 1,1-INADEQUATE experiments offer a similar look to a 1H-1H COSY experiment. However, the INADEQUATE experiments do not have diagonal and off-diagonal peaks. The 13C-13C 1,1-INADEQUATE spectrum below shows 10 carbon atoms labeled C1 to C10. The pink lines connect the adjacent C atoms. There are 3 endpoints to the pink lines at C8, C9...

Mikhail Elyashberg
To understand the molecular mechanism underlying the genus-specificity of sperm chemotaxis of ascidians (a type of marine invertebrate filter feeders), Matsumori et al have investigated the structure of a novel compound Ascidia-SAAF 2 (molecular formula C27H44O10S2Na2) isolated from the eggs of the ascidian Ascidia sydneiensis.