May 20, 1954
COMMUNICATIONS TO THE EDITOR
2841
have recently described the isolation of this analog in which the nicotinamide moiety of DPN has been replaced by INAH yielding D-INAH-N. THEROCKEFELLER INSTITUTE LYMAN C. CRAIG have reported that FOR MEDICAL RESEARCH WERNERHAUSMANN Although Zatman, et JAMES R. WEISIGER the beef spleen DPN-ase is inhibited by both INAH NEW YORK,N. Y. and D-INAH-N, we have taken advantage of the RECEIVED APRIL 12, 1954 fact that this inhibition, while marked, is incomplete. The analog, accordingly, was prepared by A NEW SYNTHESIS OF CYCLOHEPTATRIENE incubating 100 p moles of DPN (sigma "90"), 180 Sir: mg. of beef spleen D p N - a ~ e and , ~ a large excess of Methods presently available' for the preparation INAH4 (10 mmoles) for 4 hours a t 38' in 0.015 M of cycloheptatriene (I) involve ring expansion of a phosphate buffer (pH 7.4). Under these condisix-carbon cycle as the key reaction step. a r e wish tions, this amount of enzyme would normally catato report a novel and convenient synthesis of I lyze the cleavage of as much as 7,200 pmoles of which involves opening of the cyclobutane ring in a DPN. The slow rate of reaction indicates a very derivative of bicyclo [3.2.0]heptane. Reduction of strong inhibition of the enzyme, a finding which is the readily prepared (from cyclopentadiene and ke- in complete agreement with that of Zatman and cotene) bicyclo [3.2.0]hept-2-ene-B-one with lithium workers. aluminum hydride afforded (95%) bicyclo [3.2.0]The analog, after isolation by charcoal adsorphept-2-ene-6-01 (11), b.p. 96-98' (38 mm.), n Z 5 ~ tion, pyridine elution, and precipitation of the nu1.4987 (Calcd. for CyHloO: C, 76.32; H, 9.15. cleotides with cold acetone, contained about 10% Found: C, 76.20; H, 8 . 8 i ) . Treatment of I1 with DPN which was removed by incubating the isomethanesulfonyl chloride in pyridine afforded the lated nucleotide mixture with DPN-ase and INAH. methanesulfonate (111)as a crude oil which was not D-INAH-N isolated from the second exchange repurified further owing to its thermal instability. action is essentially free of DPN. Molar ratios of Solvolysis of 111 in hot acetic acid containing two the analog are shown in Table I. Extinction coefmole equivalents of sodium acetate, or preferably TABLE I sodium dihydrogen phosphate monohydrate, af-Moles per mole of D - I N A H - N p forded I in approximately 507, yield based upon 11. INAHa Riboseb P C DPNd Identification of I was made through comparison of 2.00 0.00 Theory 1.00 2.00 its physical constants (b.p. 60.5' (122 mm.), nZ5D Found 1.00 1.95 2.28
