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competes effectively with flavin radical disproportionation.The lumiflavin triplet is also able to abstract hydrogen from a ground state lumiflavin molecule (probably from the 10-methyl group). The radicals so generated can either recombine or undergo a buffer-catalyzed reaction leading to permanent bleaching.

In ethanolic solution, the intramolecular photorearrangement of azoxybenzene occurs with quantum yield close to 0.02 over the range 250-350 nm. The reaction, which is independent of temperature and of concentration of reactant, is conveniently monitored by measuring the absorbance of the product. Zhydroxyazobenzene, as its anion in alkaline solution. Am. Chem. SOC. 99, 7986-7991. ADS, 518-536. Wani (1965) J. Am. Chem. SOC. 87, 1138-1140. 'An equation comparable with Eq. 1 was developed previously (Bunce, 1981; Zimmerman er al., 1965).

acid-dichloromethane (3X4 ml). The combined filtrates were evaporated in vacuo and the residue was dissolved in water for the chromatography of Leu-Ala-Gly-Val on the long column of the Beckman 120B amino acid analyzer. The color value for Leu-Ala-Gly-Val was found to be 0.71 that of valine. The resin was resuspended in 50% trifluoroacetic acid-dichloromethane (4 ml) and shaking was continued. The combined loss of Leu-Ala-Gly-Val from the resin was determined at 4 h (14.7%), 8 h (21.7%), 16 h (34.4%), 24 h (44.3%), 32 h (52.1%), 40 h (59.3%), 48 h (65.9%), and 64 h (75.8%). Figure 1 shows a plot of the peptide remaining vs. time.Boc-Leu-Ala-Gly-Val-4-(oxymethyl)phenylacetamidomethyl-resin (100 mg, 53.8 Mmol) prepared from resin 3b was shaken with 50% trifluoroacetic acid-dichloromethane (4 ml) as described above. The combined loss of Leu-Ala-Gly-Val from the resin was monitored at 8 h (0.43%), 24 h (0.96%), 48 h (1.53%), 72 h (1.96%), and 96 h (2.26%); see Figure 1.

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