Treatment of the serine-derived organozinc reagent 2, in benzene/dimethylacetamide, with a THF solution of CuCN.2LiCI gives rise to a zindcopper reagent 6 which reacts directly with allylic halides and tosylates to give the corresponding enantiomerically pure substitution products 9 in 32-65% yield (11 examples). The reaction proceeds by formal S N~' displacement of the leaving group. Reaction with propargyl halides gives the corresponding terminal allene 12a. The zinc reagent 2 may also be prepared directly from protected iodoalanine 1 in THF by the Knochel method. Reaction with propargylic tosylates as electrophiles gives rise to the corresponding protected terminal allenic amino acids in 51-8196 yield (four examples); use of enantiomerically enriched propargylic tosylates results in the formation of diastereoisomerically enriched allenic products. Reactions of the zinc/ copper reagent 6 with a range of representative electrophiles is explored; use of relatively reactive electrophiles is necessary to obtain satisfactory yields. Finally, the possibility of using the serinederived iodide 20, in which the carboxylic acid is protected as a methyl ester, is established. This reagent offers advantages over the corresponding benzyl ester protected reagent 6 for the synthesis of unsaturated amino acids.There has been continuing interest in the development of new methods for the synthesis of enantiomerically pure a-amino acids.2 Those approaches which make use of readily available chiral building blocks, for example, by employing derivatives of serine, are especially attractive. Recent work has established that insertion of zinc into the carbon-iodine bond of protected iodoalanine 1, prepared in four steps from serine, generates a reagent 2 which can function as the synthetic equivalent of the alanine p-anion 3.3 Thus, reaction of the zinc reagent 2 with acid chlorides under palladium catalysis gave enantiomerically pure protected 4-oxo amino acids 4, while reaction with aryl iodides, also under palladium catalysis, gave protected phenylalanine derivatives -NHBoc m-NHB~~ 1 . CQBn CQBn 1 2 RCOCl Arl R-NHBoc -+'h+ CQ' 3 ~N H B o c k : CQBn 5The extensive development by Knochel of functionalized zindcopper reagents5 suggested to us that a new alanine p-anion equivalent might be available by treatment of the alanine-derived zinc reagent 2 with CuCN.2LiCL6 The enhanced reactivity of zindcopper reagents, when compared with zinc reagents, implied @ Abstract .published in Advance ACS Abstracts, March 15, 1995.(1) Visiting postgraduate student from the Institut fur Organische Chemie, Universitat Hamburg.(2) Williams, R. M. Synthesis of Optically Active a-Amino Acids; that such an amino acid derived zinclcopper reagent7 would be of value in expanding the range of enantiomerically pure amino acids which may be prepared by the alanine p-anion strategy. In this paper we present a full account of our investigations into the synthetic application of the iodoalanine derived zindcopper reagent 6.s This work has been focussed on the reac...

Mares' Non-Pregnancy .Urine.-The butanol extract of 300 gallons of mares' non-pregnancy urine (previously hydrolyzed with hydrochloric acid) was hydrolyzed with an excess of aqueous potassium hydroxide solution. The neutral fraction was extracted with ether, which on evaporation yielded 209 g. of tarry residue. This residue was dissolved in a minimum amount of ethyl alcohol and treated with a 2% digitonin ethyl alcohol solution. On decomposition of the digitonide and sublimation of the residue under high vacuum at 130-140°, 0.34 g. of cholesterol was obtained, m. p. 144-146°. There was no depression in melting point when mixed with an authentic sample of cholesterol.

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Diosgenin, isolated by Tsukamoto from the roots of Dioscorea tokoro (Makino), has been shown to be a steroidal sapogenin of structure I.1,2,3,4 Recently sarsasapogenin was converted to progesterone.6,6 An easier route to progesterone starts from diosgenin.4 This suggested the desirability of finding an American source for diosgenin.