Steroids ethynyl alcohols from

Fragmentation reactions.1 Silver carbonate on Celite (Fetizon s reagent) quantitatively cleaves steroidal 17-ethynyl alcohols. Thus treatment of 17a-ethynylestradiol methyl ether (1) with silver carbonate on Celite in toluene under reflux gives estrone methyl ether (2) in quantitative yield. In the same way, dehydroepiandrosterone (4) was obtained from (3). 0H 0... 

Lithium acetyhde also can be prepared directly in hquid ammonia from lithium metal or lithium amide and acetylene (134). In this form, the compound has been used in the preparation of -carotene and vitamin A (135), ethchlorvynol (136), and (7j--3-hexen-l-ol (leaf alcohol) (137). More recent synthetic processes involve preparing the lithium acetyhde in situ. Thus lithium diisopropylamide, prepared from //-butyUithium and the amine in THF at 0°C, is added to an acetylene-saturated solution of a ketosteroid to directly produce an ethynylated steroid (138). 

The stereochemistry of the product resulting from the reaction of a 17-keto steroid with ethylidenetriphenylphosphorane is different from that of the 17-ethylidene steroids obtained by dehydration of 17a-ethyl-17/ -hydroxy compounds, Wolff-Kishner reduction of A -20-keto steroids or by sodium-alcohol or sodium-ammonia " reductions of 17-ethynyl carbinols. These latter products have generally been assumed to possess the trans configuration (C-21 methyl away from the bulk of the ring system) because of anticipated greater stability. The cis configuration for... 

In the laboratory of E.J. Corey, the first synthesis of nicandrenones (NIC), a structurally complex steroid-derived family of natural products, was accomplished. The side chain of NIC-1 was constructed from the known six-membered lactone which was converted to the Weinreb s amide by treating it with excess MeNH(OMe) HCI and trimethyl-aluminum. The resulting primary alcohol was protected as the TBS ether. The ethynylation of this amide was carried out by reaction with two equivalents of lithium trimethylsilylacetylide to afford an ynone, which was reduced enantioselectively to the corresponding propargylic alcohol using CBS reduction. 

Androsta-l,4-diene-3,17-dione reacted selectively at C-17 with potassium acetylide to give the 17a-ethynyl-17/8-alcohol the dihydroxyacetone side-chain was then elaborated by use of known transformations, without interference from the l,4-dien-3-one system/ Ethynylation of a [16- H]- or [16- H2]-17-oxo-steroid proceeds without loss of label/ ... 

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