A crucial step in the Baldwin and Whitehead proposal for explaining the biogenesis of the marine alkaloid manzamine A is the selective oxidation of natural keramaphidin B to an iminium salt 3, which is then hydrolyzed to give the aldehyde 4. Conditions are now presented in which this selective oxidation can be performed on model compound 8, leading to the iminium salt 16. Although this salt can be considered as a model equivalent of the proposed aldehyde intermediate 4, it was found to be very resistant to hydrolysis as was the corresponding amide 20. From a synthetic point of view, the reported results illustrate the usefulness of the temporary protection of tertiary amines as aminoborane derivatives and constitute a good method for the oxidation of a sterically hindered tertiary nitrogen atom in the presence of a second nitrogen.

The minor surgery performed at our health centre by our team was more cost-effective than if it was performed in other public or private centres with high standards of quality.

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A 47-year-old man came to the hospital because acute abdominal pain and vomits. The patient had suffered from episodes of intestinal obstruction since adolescence, and has been studied by a gastroenterologist who found no abnormalities. These episodes have been solved spontaneously in nearly all occasions. However, he had come to the emergency room for the same reason twice last year. The exploration showed abdominal distension and tympanism in the epigastrium. There were neither laparotomic scars nor hernia defects in the abdominal wall. Abdominal X-rays showed air-fluid levels at the small bowel, and marked distension in the proximal and medium jejunum. Gastrointestinal X-ray series with gastrographin showed no abnormal findings. After 48-72 hours the patient persisted with the same complaints, and we decided to operate. During the operation we found a congenital malformation: an intestinal hernia of jejunum inside a peritoneal sac formed by a peritoneal flap of the left mesentery (Fig. 1), as well as an abnormal implantation of the mesentery above the rectum. We performed a resection of the peritoneal sac (Fig. 2) and the adherences inside it. The postoperative period was normal. DISCUSSIONParaduodenal hernias are rare congenital malformations, but they are the most frequent cause of internal hernias (50% of them). They are caused by a failure in the intestinal rotation, and by an asynchronism in the future development of adhesion of the mesocolon. In right paraduodenal hernias, the small bowel is placed totally or partially behind the ascending mesocolon; in left paraduodenal hernias or mesocolic hernias, which are more frequent than the right ones, the small bowel is placed behind the descending mesocolon (1). We present a rare case of a paraduodenal sac formed by a peritoneal