Synthesis and hSERT activity of homotryptamine analogs. Part 6: [3+2] dipolar cycloaddition of 3-vinylindoles
Lawrence R Marcin1, Ronald J Mattson, Qi Gao
1Bristol-Myers Squibb, Research and Development, 5 Research Parkway, Wallingford, CT 06492-7660, USA.
Abstract:
Substituted 1-tosyl-3-vinylindoles undergo [3+2] dipolar cycloaddition with cyclic nitrones to afford substituted isoxazoles in good yield and high diastereoselectivity. The cycloadducts were readily converted in 4 steps into ring constrained homotryptamine analogs. These analogs exhibited excellent binding affinity for the human serotonin transporter (hSERT). Indoles bearing a 5-cyano group and a pendent ethyl(tetrahydroisoquinoline) moiety at the 3-position displayed the best potency for hSERT and high selectivity versus hDAT and hNET.
Related Concept Videos
Cycloaddition Reactions: Overview
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Cycloaddition Reactions: MO Requirements for Thermal Activation
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.


![Solid-phase Synthesis of [4.4] Spirocyclic Oximes](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F58508.jpg&w=3840&q=50)