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Thứ Ba, 5 tháng 8, 2025

Compounds of the week

on tháng 8 05, 2025 0 Comment

Isocarbacyclin

Isocarbacyclin¹ is a synthetic analogue of prostacyclin², a natural lipid that functions as a vasodilator and inhibitor of platelet aggregation. In 1983, Masakatsu Shibasaki, Yasuhiro Torisawa, and Shiro Ikegami*at Teikyo University (Sagamiko, Japan) reported the first synthesis of isocarbacyclin and showed that it was a more potent inhibitor than prostacyclin.

In 1990, Tadakatsu Mandai, Seiki Saito, and co-workers at Okayama University of Science (Japan) reported a highly efficient method for synthesizing isocarbacyclin. Beginning from the available (4S)-4-(tert-butyldimethylsiloxy)-2-cyclopenten-1-one, the authors assembled the two rings in the reverse order from that of earlier syntheses. A key step was a single-pot, three-step tertiary allylic vinyl ether formation, Claisen rearrangement, and ene cyclization that completed the bicyclic framework.

Almost 30 years later, Ghina’a I. Abu Deiab and Mitchell P. Croatt at the University of North Carolina at Greensboro described a synthesis of isocarbacyclin in nine steps from commercially available starting materials. Their key steps were a palladium(0)-catalyzed decarboxylation, a rhodium(I)-catalyzed cycloaddition, and a ruthenium(II)-catalyzed cross-metathesis reaction. Isocarbacyclin analogues with alternative side chains were made in seven to ten steps.

In addition to its greater efficacy than prostacyclin, isocarbacyclin is more stable than its natural counterpart. Because it inhibits platelet aggregation, it can be used for treating ischemic stroke to prevent nerve damage. As a vasodilator, it has also been studied for treating vascular disorders such as thromboangiitis obliterans and arteriosclerosis obliterans. Despite the progress in this research, a large-scale synthesis of Isocarbacyclin has yet to be developed.

1. SciFinder name: 2-pentalenepentanoic acid, 1,3a,4,5,6,6a-hexahydro-5-hydroxy-6-[(1E,3S)-3-hydroxy-1-octenyl]-, (3aS,5R,6R,6aS)-.
2. CAS Reg. No. 35121-78-9.

Isocarbacyclin hazard information*

Hazard class**	GHS code and hazard statement
Acute toxicity, oral, category 4	H302—Harmful if swallowed
Skin corrosion/irritation, category 3	H316—Causes mild skin irritation
Serious eye damage/eye irritation, category 1	H318—Causes serious eye damage
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3	H335—May cause respiratory irritation

*No SDS available online. Data taken from AI search.
**Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.

MOTW updates

Prednisone¹ and methotrexate² were the Molecules of the Week for June 22, 2009, and January 16, 2012, respectively. Prednisone is a glucocorticoid anti-inflammatory agent that must be used carefully because it is also an immune system suppressant. Methotrexate is a chemotherapy drug that blocks the body’s use of folic acid, but it has several side effects.

This past May, Marlies S. Wijsenbeek at the University Medical Center (Rotterdam, the Netherlands) and 22 collaborators there and at other Dutch institutions reported the results of a study of prednisone versus methotrexate as a first-line treatment of pulmonary sarcoidosis, a disease that causes abnormal collections of inflammatory cells in the lungs. Previous work assigned prednisone as a first-line treatment despite its many side effects and methotrexate as a second-line treatment, also with side effects but with a slower onset of action. The results of the authors’ 138-patient, 24-week study showed that both drugs performed equally well and that the decision between the two should be made based on the side-effect profile for each patient.

Benzene³ is the simplest six-carbon aromatic molecule and was the Molecule of the Week for July 3, 2023. It is a useful solvent and reagent but is carcinogenic and therefore less used than in the past.

The benzene ring is extremely stable; and many attempts have been made to open it under relatively mild conditions. Last month, Xiaotai Wang at Xi’an Jiaotong-Liverpool University (Suzhou, China), Jiaxiang Chu at the University of Chinese Academy of Sciences (Beijing) and Binzhou Institute of Technology (Shandong, China), and co-workers at these institutions reported the room-temperature ring opening of benzene via a four-electron reduction and carbonylation reaction. The four-electron reagents used were reduced scandium arene complexes with chromium, molybdenum, or tungsten hexacarbonyls. The resulting products were linear hexadienes bound to scandium–metal oxygenates derived from the complexes. The authors followed up by obtaining comparable results with toluene.

1. CAS Reg. No. 53-03-2.
2. CAS Reg. No. 59-05-2.
3. CAS Reg. No. 71-43-2.

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Source: ACS