sponge collection and identification. High resolution mass spectra were provided by the mass spectrometry facility at Massachusetts Institute of Technology, supported by a grant (principal investigator, Professor K. Biemann) from the Biotechnology Research Branch, Division of Research Resources. We gratefully acknowledge grants from the Phillips Petroleum Co., Bartlesville, Okla., and the NSF (G P 38410) which aided in the purchase of NMR spectrometers.

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It was recently reported that base-promoted reaction of cyclobutanone with dialkyl (diazomethy1)phosphonates (DAMP) afforded cyclopentyne (eq l).'qz One part of that study involved I production of a [2 + 21 cycloaddition product 1 between the alkyne and dihydrofuran, a reaction first reported by Fitjer et al.4 The present report defines the stereochemistry of this type of cycloaddition.Reaction of cyclobutanone, the anion of DAMP (generated with KH at -78 "C), and cis-l-meth~xy-l-propene~*~ afforded a cycloadduct which was isolated by HPLC and characterized by standard spectroscopic methods as being 2.' Most relevant to J . Am. Chem. Soc.Foundation (F-815) for this research is gratefully acknowledged. We thank Dr. Steven Larson for the X-ray crystallographic results and Kevin Sweeney for GC-MS analyses.Supplementary Material Available: ORTEP structure, crystallographic data, and bond lengths and angles for adduct 5 (3 pages). Ordering information is given on any current masthead page.Ribonucleotide reductase (RDPR)' from E . coli catalyzes the conversion of nucleoside diphosphates to deoxynucleoside diphosphates.2 This enzyme is composed of two subunits: B, (a, a' M , 160000) binds NDP' substrates and contains redox active thiols and binding sites for the allosteric effectors; B2 (P,P M ,

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Paper 2/05392F