Ethyl Tosyl-L-isoleucylg1ycinate.-A solution of tosyl-Lisoleucyl chloride (prepared from 2.9 g. of tosyl-L-isoleucine and-phosphorus pentachloride) in r5 ml. of anhydrous ether was added slowly to a suspension of 2.5 g. of ethyl glycinate hydrochloride and 3.5 ml. of triethylamine in 50 ml. of anhydrous ether and the mixture was allowed to stand at room temperature for 12 hours. The white precipitate was filtered off and washed with ether. After trituration with water to remove the triethylamine hydrochloride, 3.34 g. of product, m.p. 159-160°, was obtained; yield 89%. Another 0.25 g., m.p. 152-154', was afforded by extraction of the ether filtrate successively with water, dilute HCl, dilute aqueous KHCO, and water, followed by removal of the ether zn vacuo. Recrystallization of the second crop from ethanol raised the m.p. to 158-160". For analysis, the tosyl dipeptide ester was recrystallized twice from ethanol and then melted a t 160-161".

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SynopsisTriplet-triplet energy transfer has been shown to occur from poly(ethy1ene terephthalate) (PET) units to the 2,6-naphthalenedicarboxylate (2,6-ND) monomer units in a series of poly(ethy1ene terephthalate-co-2,6-naphthalenedicarboxylate) (PET-2,6-ND) copolymers, as filament yarns, by an exchange mechanism a t 77OK. The radius of the "quenching sphere" has been calculated to be 19.7 A, indicating the presence of triplet energy migration. Photostabilization was observed in the copolymer yarns with the concentration of the monomer dimethyl 2,6-naphthalenedicarboxylate (2,6-DMN) at or above 2 mol % the rate of phototendering in an air atmosphere was shown to decrease from 2.0 X 10-19% breaking strength loss/quantum absorbed/cm* in the homopolymer PET to 0.7 X 10-'9% breaking strength loss/quantum absorbed/cm2 in the copolymer yarns. The photophysical processes in the monomers, dimethyl terephthalate and 2,6-DMN, were examined by absorption and luminescence studies. The lowest excited singlet and triplet in both monomers were identified to be the '(T,T*) and 3(7r,7r*) states, respectively. The phosphorescence of PET was shown to originate from a 3 ( 7 r ,~* ) state, while the complex fluorescence spectrum may arise from some oriented aggregates in the polymer matrix. In copolymer yarns, only the fluorescence emission from the 2,6-ND monomer units at 380 nm was observed. The phosphorescence spectra of the COpolymer yarns showed phosphorescence emissions from the PET and 2,6-ND monomer units; in addition, delayed fluorescence from the 2,6-ND monomer was also observed.

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In a previous communication the synthesis of various alkylated pentamethylenetetrazoles was described (1). The activity of pentamethylenetetrazole (Metrazol) as an analeptic and respiratory stimulant was enhanced by the substitution of alkyl groups in the pentamethylene ring (2). In continuing our studies of the effect of structure on the pharmacologic activity in the tetrazole series it became of interest to determine whether similar relationships existed in a series of simple 1,5-disubstituted tetrazoles (I). Although a number of such structures in which one of the substituents on the tetrazole ring is an aromatic group are known (3), only a single example, 1,5-dimethyltetrazole, in which both substituents are aliphatic in character has been described.