A general synthesis from -tropolone methyl ether of natural and modified prostaglandins is detailed. A key intermediate in the synthesis, 7-methoxybicyclo[3.2.0]hepta-3,6-dien-2-one, has been secured from a-tropolone methyl ether in improved yield and converted to an array of natural and modified prostaglandins through the use of a number of regio-and stereoselective reactions. In several instances, proof of structure and stereochemistry has been obtained through conversion of PGA2 from the marine coral Plexaura homomalla to the synthetically derived products.

The nitrolysis of N-butyk/V-fluorocarbamate most likely proceeds by the electrophilic displacement of carbomethoxycarbonium ion by nitronium ion (eq 3).C4H9NFCOOCH3 + NOa+-C4H9NFN02 + l+COOCHs] (3)This mechanism is analogous to that proposed for the fluorinalysis of N-alky 1-A-fluorocarbamates to the corresponding , -difluoroalkylamines.9 The nitrolysis of iV,jV-dialkylformamides has also been reported.10 Experimental SectionFluorinations were conducted in a three-necked flask following the previously described technique.5 Adequate safety shielding should be used when handling N-fluoro-JV-nitrobutylamine.Fluorination of Butylnitramine.-Butylnitramine (11.8 g, 0.1 mol) and 0.1 mol of potassium hydroxide in 250 ml of water were fluorinated with 0.1 mol of fluorine over a period of 45 min. A yellow liquid separated. The product was extracted with 70 ml of methylene chloride, and was washed with 75 ml of cold saturated aqueous sodium bicarbonate and 75 ml of water. The methylene chloride solution was dried with sodium sulfate and distilled to give 11.5 g (86% yield) of N-fluoroJV-nitrobutylamine: bp 40°( 25 mm); proton nmr (CC14) S 0.98 (m,

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Food Reseach Institute (Norwich, England) Mass Spectrometry Group for obtaining all the high resolution, and a good part of the low resolution, mass spectral data; to M. W. Johnson of the John Innes Institute (Norwich, England) for the high resolution computer program; and to B. J. Gordon, F. R. I. Mass Spectrometry Group, for the low resolution computer program used in this work.87 (37) Some preliminary precise mass determinations on a few ions were made by R.