Issam Hanna

Gold(I)-Catalyzed Cycloisomerization of 1,7- and 1,8-Enynes: Application to the Synthesis of a New Allocolchicinoid

Gold(I)-catalyzed cycloisomerization of 1,7- and 1,8-enyne propargylic acetates afforded cyclopropyl derivatives containing seven- and eight-membered rings, respectively. This reaction was used for the synthesis of a new allocolchicinoid having a cyclopropane ring fused to the B seven-membered ring at the C6-C7 positions.

Toward the total synthesis of vinigrol: synthesis of epi-C-8-dihydrovinigrol.

Two approaches to vinigrol starting from the advanced tricyclic core 7 have been explored using as key intermediates epoxide 12 and diol 17. The preparation of the properly functionalized epoxide 12 has been achieved in a straightforward fashion. However, all attempts to prepare tertiary alcohol 14 by reductive opening of 12 failed. In alternative exploratory efforts to achieve the same goal, allylic alcohols 16 and 29 were prepared by regioselective dehydration of diol 17. Whereas endo-isomer 16 was found to be reluctant to undergo catalytic hydrogenation, the exo counterpart 29 led to the undesired isomer affording after hydrolysis epi-C-8-dihydrovinigrol 32.

An expeditious construction of polycyclic ketals: synthesis of fused seven-membered rings and substituted naphthalenes

Abstract Treatment of allylic alcohols 5 , easily prepared from dioxene and methoxyacetophenones, with 1-(trimethylsilyloxy)cyclopentene in the presence of a catalytic amount of TMSOTf in acetonitrile, afforded a polycyclic acetal 6 by domino nucleophilic substitution, annulation and intramolecular Friedel–Crafts alkylation reaction sequence. Acid-mediated cleavage of the acetal moiety led to fused seven-membered carbocyclic rings or to substituted naphthalenes.

1,4-Dioxene(2,3-dihydro-1,4-dioxine) in organic synthesis. Part 9. Preparation of biologically active side-chains from 17-oxosteroids

Steroidal 17α-2,3-dihydro-1,4-dioxin-6-yl)-17β-ols of type (2), readily available from 17-oxo steroids and 2 3-dihydro-1,4-dioxine, are easily converted into 21-hydroxy-20-oxo steroids with or without a double bond at the 16(17) position as well as to the dihydroxyacetone side-chain.