Related Experiment Video
Updated: Jun 1, 2026
06:00
One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates
Published on: January 15, 2018
Redetermination and absolute configuration of 7α-hy-droxy-royleanone
Summary
This study redetermined the crystal structure of an abietane diterpenoid from Premna obtusifolia roots using copper radiation. The absolute configuration was definitively established, revealing specific stereogenic centers and intermolecular interactions.
Area of Science:
- Natural Product Chemistry
- Organic Chemistry
- Crystallography
Background:
- An abietane diterpenoid, C(20)H(28)O(4), was isolated from Premna obtusifolia roots.
- Previous crystal structure analysis using Molybdenum radiation failed to determine the absolute configuration.
Purpose of the Study:
- To redetermine the crystal structure of the title compound.
- To definitively establish the absolute configuration of the stereogenic centers.
Main Methods:
- Single-crystal X-ray diffraction analysis using Copper radiation.
- Analysis of intra-molecular hydrogen bonds (O-H⋯O) and C-H⋯O contacts.
- Investigation of crystal packing and intermolecular interactions.
Main Results:
- The absolute configurations of stereogenic centers at positions 4b, 8a, and 10 were determined as S, S, and R, respectively.
- Two intra-molecular hydrogen bonds forming S(5) and S(6) rings were identified.
- Molecules form infinite chains in the [100] direction via O-H⋯O hydrogen bonds and C-H⋯O interactions.
Conclusions:
- The absolute configuration of the abietane diterpenoid from Premna obtusifolia has been unambiguously determined.
- Detailed analysis of hydrogen bonding and crystal packing provides insights into the compound's solid-state structure.
Related Concept Videos
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
02:33Stereoisomerism of Cyclic Compounds
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
01:12Stereochemical Effects of Enolization
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound undergoes racemization under an acidic or basic condition, an achiral enol is formed.
02:36Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
02:05Prochirality
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...