Beautiful Panorama Research Articles

Recent Advances in the Chemistry of Natural Products

It gives me great pleasure to exercise this opportunity to present to you some of the results of a collaborative investigation which has as one of its objectives the synthesis of vitamin B12. These studies have been pursued in my laboratory at Cambridge and in that of Albert Eschenmoser at Zurich. They have been prosecuted on a very broad front, and in the limited time available here it will be possible to describe only a small portion. of the work. I have chosen to present those results which seem to us at present most surely destined to constitute established stages in the achievement of the specific objective of synthesizing vitamin B,2. To make this choice is not to derogate the interest and fascination of other portions of the investigation. Indeed, before embarking on today's story, I permit myself a parenthesis. The history of organic chemistry provides in abundance instances of the major role played by the study of natural products in revealing, extending, and shaping the fundamental bases of the science. Time and again the penetration of a new sector of the vast, often surprising and always beautiful panorama of natural products has led to new insights which could hardly have been achieved by more self-conscious fundamental investigations. This role of natural product studies is in no way diminished in our day, and it will certainly continue in the future; the proposition cannot be better illustrated than by my alluding to the fact that the principle of orbital symmetry conservation arose directly from our studies on vitamin B12 synthesis. But that story has been outlined in another place', and I shall have nothing further to say about it today. Let us commence by scrutinizing the structure of the vitamin B12 molecule (I). That intricate and fascinating array, revealed to us by the beautiful x-ray crystallographic studies of Dorothy Hodgkin, exhibits certain resemblances to other natural substances. Thus, like the blood pigment, haem, and the leaf pigment, chlorophyll, it contains a metal atom embedded within a macrocyclic nucleus containing four five-membered heterocyclic rings— A, B, C and D. But while in the blood and leaf pigments these five-membered rings are held together by single-carbon bridges, in the case of vitamin B12 two of them, rings A and D, are directly linked. Above all, the most striking contrast between vitamin B12 and its more simply constituted relatives, haem and chlorophyll, lies in the realm of stereochemistry. The porphyrin nucleus of the haem molecule is constituted entirely of trigonal carbon atoms and presents no points of stereochemical interest; the dihydroporphyrin, or chlorin, nucleus of chlorophyll presents only the relatively trivial stereochemical problem associated with the presence of two unsymmetrically substituted tetrahedral carbon atoms. In striking contrast, the periphery

THE IMPRESSIONS OF A DIETITIAN IN THE NAVY

is a very attractive Naval Hospital, situated on a hill studded with stately pine trees, from which can be seen a beautiful panorama embracing snow-capped mountain ranges; Puget Sound, that picturesque inland sea with its irregular coast line, and the artistic towns built upon the hillside along the shore. In this pleasant environment fifteen congenial Navy nurses are endeavoring to do their bit working cheerfully in the wards, operating room, laboratory, or wherever they may be assigned by the most considerate of commanding officers. The routine duties of a Naval Hospital are the same at all posts, we instruct the hospital corps men in the care of the sick, both practically and theoretically, in the same manner that we would teach pupil nurses in a civilian hospital, and the more conscientiously we do our duty as instructors, the larger the area which our usefulness will spread, as these hospital corps men go forth to the battleships with the instruction which we have imparted to them, and are the nursing medium in saving numbers of lives. In leisure hours, some of our number study French, with preparedness as their motto; others are musically inclined, practising on the mandolin, ukelele, and cther instruments; soon we may have a Jazz band of our own. Then the alluring attractions of the Sound, bathing, boating and fishing, help to enliven our spare moments. Entertainments are given at the Armory of the Navy Yard, where all may enjoy the best talent, and last, but not least, are the weekly dances chaperoned by the charming wife of the Commandant of the Navy Yard. Why not join our merry company? The U. S. N. Nurses of Puget Sound Naval Hospital will give you a cordial greeting. Perhaps our work has not the stimulus of the unusual which may be found by the nurses who have gone over there but the service is just as creditable and just as necessary.