We report an efficient solid-phase synthesis of diverse 1,3N-disubstituted quinazoline-2,4-diones. Since substitutions at the 1N-position of quinazolidine-2,4-diones were introduced by reaction between primary amines and 2-fluoro-5-nitrobenzoyl amides (S N Ar reaction), substitutions that cannot be prepared by alkylation or arylation can be easily introduced. In addition, the nitro group of quinazoline-2,4-diones can be repeatedly reduced to provide 3N-amines for quinazoline-2,4-dione syntheses, allowing the synthesis of quinazoline-2,4-dione oligomers and polymers. An oligomer with four quinazoline-2,4-dione units was successfully synthesized.

The synthesis of 2,3,5-triketopiperadines on solid-support has been achieved for the first time. Cyclization of 4 using oxalyl diimidazole proceeded excellently with N-methyl amino acids except for Sarcosine (Sar). On the other hand, this cyclization did not proceed well when amino acids without N-methyl substitution were used. This can be explained by the lower energy difference between the trans and cis configurations of oxalyl amide 5 by the introduction of N-methyl substitution, because cis conformation is necessary for the cyclization to proceed. This cyclization also worked well with amino acids with a six-membered ring such as tetrahydroisoquinoline-3-carboxylic acid (Tic) and piperidine-2-carboxylic acid (Pic), which are N-alkylated amino acids. Although the purity of the target compounds was found to be low in the case of Sar and amino acids with a five-membered ring such as proline (Pro) and thiazolidine-4-carboxylic acid (Thz) under the same cyclization conditions, we were able to successfully optimize the reaction conditions to give the target compounds with good purity. Furthermore, it was demonstrated that 2,3,5-triketopiperadines with three points diversity could be prepared on solid-support with high purity, showing the generality of this method.

From the homogenate of rat submaxillary gland, two kinds of serine proteinases, named tentatively proteinases A and B, were isolated and their chemical properties and activities toward rat kininogens were examined, in comparison with those of submaxillary kallikrein. Proteinase A with Mr of 28,200 rapidly cleaved high-molecular-weight (HMW) kininogen into a protein of 67 kDa, which retained thiol-proteinase inhibitory activity, but had lost the correcting activity of HMW kininogen on the prolonged clotting time of Fitzgerald trait plasma. It liberated bradykinin from HMW kininogen but did not liberate kinin from T-kininogen and did not degrade T-kininogen. On the other hand, proteinase B with Mr of 30,400 showed a very weak activity for the liberation of kinin from T-kininogen and the cleavage of T-kininogen at pH 8.0. However, the enzyme extensively degraded T-kininogen at pH 4.5. Proteinase B also degraded HMW kininogen at pH 4.5 and pH 8.0, but liberated bradykinin only at pH 8.0. Thiol-proteinase inhibitory activities of HMW kininogen and T-kininogen were inactivated after the incubation with proteinase B at pH 4.5 but not at pH 8.0, while the correcting activity of HMW kininogen on the Fitzgerald trait plasma was inactivated at pH 4.5 and 8.0. The NH2-terminal amino acid sequences of proteinases A and B were different from each other, and distinguishable with those of serine proteinases in rat submaxillary gland so far reported. These results provide evidence that in addition to the known kallikrein, there exist at least two kinds of serine proteinases in rat submaxillary gland, both of which liberate bradykinin from rat HMW kininogen at pH 8.0 and modulate the functional activities of HMW kininogen and T-kininogen, degrading these proteins at pH 8.0 or 4.5.

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