1. Synthesis of the Tricyclic Ring Structure of Daphnanes via Intramolecular [4 + 3] Cycloaddition/SmI2‑Pinacol Coupling
Ahmed H. E. Hassan,†,‡,§ Jae Kyun Lee,†,‡ Ae Nim Pae,†,‡ Sun-Joon Min,*,†,‡ and Yong Seo Cho*,†,‡
† Center for Neuro-Medicine, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
‡ Department of Biological Chemistry, Korea University of Science and Technology (UST), Daejeon
Republic of Korea § Department of Medicinal Chemistry, Faculty of Pharmacy, University of Mansoura, Egypt
Org. Lett. 2015, 17, 2672−2675

2. Daphnane diterpenoids, mainly found in Thymelaeaceae and Euphorbiaceae
To date, more than 100 daphnane diterpenoids have been isolated from nature showing a wide range of biological activities skin irritant, anti-HIV, cytotoxic, antileukemic, and neurotrophic effects
resiniferatoxin (1) exhibits an analgesic effect through activation of transient receptor potential vanilloid 1 (TRPV1), which induces desensitization of nociceptive neurons
Kirkinine (2) functions as a potent neurotrophin that promotes neuronal survival
only total syntheses of resiniferatoxin and yuanhuapin were completed by Wender and co-workers.

3. desired exo isomer was predominantly acquired through epimerization
4-silyloxypentadienal
Michael Harmata et al., J. Am. Chem. Soc., 2003, 125 (8), pp 2058–2059
An intramolecular [4 + 3] cycloaddition reaction of furan with an oxypentadienyl cation
desired exo isomer was predominantly acquired through epimerization
formation of the five-membered ring was achieved through SmI2-mediated pinacol coupling

4. sickle shape
W-type shape

5. 4- oxopent-2-enoic acid

7. X-ray crystal structures of 5a and 5c.
Published in: Ahmed H. E. Hassan; Jae Kyun Lee; Ae Nim Pae; Sun-Joon Min; Yong Seo Cho; Org. Lett.  2015, 17,
DOI: /acs.orglett.5b01054
Copyright © 2015 American Chemical Society

8. Proposed transition state for the formation of 5c.
Published in: Ahmed H. E. Hassan; Jae Kyun Lee; Ae Nim Pae; Sun-Joon Min; Yong Seo Cho; Org. Lett.  2015, 17,
DOI: /acs.orglett.5b01054
Copyright © 2015 American Chemical Society

9. Published in: Ahmed H. E. Hassan; Jae Kyun Lee; Ae Nim Pae; Sun-Joon Min; Yong Seo Cho; Org. Lett.  2015, 17,
DOI: /acs.orglett.5b01054
Copyright © 2015 American Chemical Society

10. Pfitzner−Moffatt oxidation
other oxidation reactions failed
The Dess-Martin oxidation of diol afforded keto aldehyde 18 via oxidative cleavage
Pfitzner−Moffatt oxidation