Unexpected racemization of proline or hydroxy-proline phenacyl ester during coupling reactions with Boc-amino acids

When L-proline or O-benzyl-trans-4–hydroxy-L-proline phenacyl ester was coupled with Boc-amino acids in dimethylformamide using water-soluble carbodiimide (WSCI) in the presence of anhydrous 1-hydroxybenzotriazole (HOBt) as coupling reagents, extensive racemization was observed at the Cα of the proline or hydroxy-proline residue. The extent of racemization was measured by HPLC after the coupling with Boc-L-Leu-OH in the presence or absence of HOBt. The extent of racemization increased when HOBt was added to the reaction mixture, but greatly decreased when it was not, indicating that HOBt was needed for inducing racemization. Almost no racemization was observed when the coupling reaction was carried out by the mixed anhydride procedure in tetrahydrofuran or by the carbodiimide method in dichloromethane without using HOBt. In the case of coupling reactions with ordinary L-amino acid phenacyl esters, no racemization was observed. Examination of some model systems yielded sufficient evidence to prove that HOBt is an efficient catalyst for racemizing proline or hydroxy-proline phenacyl ester not only in the stage of cyclic intermediate formation but also in the opening of the ring structure. Thus, the racemization reaction was found to be closely related to the formation of the cyclic carbinol-amine derivative.     

Case Report: Multiple Cancers: Hepatocellular carcinoma and adenocarcinomas of the common bile duct and the gall-bladder in a woman with primary biliary cirrhosis

We present a case of primary biliary cirrhosis associated with simultaneous triple cancers: a hepatocellular carcinoma and adenocarcinomas of the common bile duct and gall-bladder. A 70 year old Japanese woman, who had been diagnosed with primary biliary cirrhosis (stage 2 by Scheuer) 15 years before, was admitted to Koseiren Kamo Hospital in a comatose state. Laboratory data were as follows: the ammonia level was high (164.0 μg/dL), the antimitochondrial antibody showed a 320-fold increase, a high level of alpha-fetoprotein was indicated (2677 ng/mL), hepatitis B surface antigen was negative and hepatitis C antibody by enzyme immunoassay was negative, although a test for the RNA of hepatitis C virus by polymerase chain reaction was positive (10^3.5 copies/50 μL). The patient's condition gradually worsened and the patient died of liver failure. Autopsy showed triple cancers in the liver (hepatocellular carcinoma; trabecular type, moderately differentiated), the common bile duct (well-differentiated papillary adenocarcinoma) and the gall-bladder (well-differentiated papillary adenocarcinoma) with primary biliary cirrhosis (stage 4). Primary biliary cirrhosis has been believed to be a low risk for the development of hepatocellular carcinoma, despite the high risk of extrahepatic malignancy. The simultaneous occurrence of triple cancers with primary biliary cirrhosis, to the best of our knowledge, has never been reported. The present case may provide additional evidence for a predisposition to malignancy in primary biliary cirrhosis.     

Histopathological Features of Plasma Cell Dyscrasia with Polyneuropathy and Endocrine Disturbances, with Special Reference to Germinal Center Lesions

The biopsy and autopsy materials of 41 cases showing clinicalmanifestations consistent with those of plasma cell dyscrasiawith polyneuropathy and endocrine disturbances were studiedby light microscopy and immunohistochemistry. The results obtainedare as follows: 1) Lymph node swelling was generalized and thesize of the nodes varies up to that of a thumb tip. 2) Angiosclerosisin the germinal centers of swollen lymph nodes is one pathognomonicfeature in this disorder and was common to all the cases examinedand occurred in the early stage. 3) The other feature is monoclonalproliferation of plasma cells (plasmacytoma) occurring not onlyin the bone marrow (five biopsy cases, seven autopsy cases)but also in the lymph nodes (nine biopsy cases, four autopsycases). 4) If all the bone lesions detected roentgenologicallyare regarded as being due to monoclonal proliferation of plasmacells, it was demonstrated in 26 of 31 biopsy cases (84%) andin 14 of 16 autopsy cases (88%). This suggests that the plasmocytomaparticipates in the development of clinical manifestations ofthe disorder. 5) Besides the characteristic lesions in the lymphnodes, proliferation of small blood vessels and hemangioma-likelesions were found in the spleen, subcutaneous connective tissueand visceral adipose tissues, and hemangiomatous verrucae werealso seen in the skin. As to the pathogenesis of the vascularlesions, vasculitis may be suggested. 6) The his-tologic featuresin the other organs and tissues seem to be closely related tothe development of varied clinical manifestations and are representedby atrophy in the sural nerves, gastrocnemius muscles, and endocrineor reproductive organs.