7-O-Galloyl-D-sedoheptulose (1) was isolated in our laboratory from the water extract of the fruit of Cornus officinalis Sieb et Zucc. by bioassay-guided fractionation. In in vitro test, 1 could dose-dependently inhibit spontaneous and Con A-induced proliferation and antibody production response of splenocytes of C57 mice, indicating that it has notable immunosuppressant activity. The content of 1 in the fruit of C. officinalis is very low. In order to thoroughly investigate the pharmacological activities and mechanisms of 1, we tried to establish a synthetic approach toward this compound and its analogues.  Saccharides are poly-hydroxyl compounds. Selective protection of hydroxyl groups is a precondition for the synthesis of 1, in order to specifically connect a galloyl group at 7-OH of sedoheptulose. The obtainable form of sedoheptulose is its dehydration product, 2,7-anhydro-D-sedoheptulose (2), normally isolated from plants of the Crassulaceae family. In this study, we isolated the total saccharides from Sedum sarmentosum Bunge and Orostachys fimbriatus (Turcz.) Berger. Compound 2 was obtained after dehydration of the total saccharides under strong acidic condition.  Using 2 as the starting material, after protecting the hydroxyl groups and opening the internal acetal of 2, the 7-OH could be specifically acylated. Hydroxyl group is normally protected by forming its esters or acetal. Since the target product 1 is a gallic acid ester and the starting material 2 contains a very stable internal acetal structure, ester or acetal protecting groups could not be used in the synthesis of 1. Therefore to find a suitable protecting group is one of the difficult problems in this study; the other problem is to find an appropriate reagent which can efficiently open the internal acetal. In the practice, we probed three synthetic routes.  In the first route, the internal acetal of 2 was expected to be opened in strong acidic media such as HC1, CF_3COOH and H_2SO_4, and forming a thioacetal by reacting with ethyl mercaptan. But the expected poduct was not obtained.  In the second route, the ring opening reaction of 2 was explored at first. The Lewis acids Me_3SiI, anhydrous ZnCl_2 and BF_3·Et_2O, as well as HCl, CF_3COOH and the ion exchange resin Dowex 50-W (H~ ) were tested for their catalytic effects on the ring opening reaction of per-acetylated 2 in acetic anhydride. It was found that only BF_3·Et_2O could effectively open the internal acetal structure. Thereafter, the hydroxyl groups of 2 were protected using benzyloxycarbonyl groups, the protected product was subjected to ring opening reaction catalyzed by BF_3·Et_2O, and two compounds were obtained and identified as 1,3,4-tri-O-benzyloxycarbonyl-2-O-acetyl-D- sedoheptulose 5,7-carbonate (10) and 3,4,5-tri-O-benzyloxycarbonyl-7-O-acetyl-D- sedoheptulose 1, 2- carbonate (11). The effort to hydrolyze the 5,7-carbonate group of 10, in order to release the 7-OH for galloylation, did not succeed.  In route three, benzyl was selected as protecting group. After per-benzylation of 2 and opening the internal aetal under the catalysis of BF_3·Et_2O by strict controlling the amount of BF_3·Et_2O, the temperature and reaction time, 1,3,4,5-tetra-0-benzyl-2,7-di-O-acetyl-D-sedoheptulose(15) was obtained. Deacetylation of 15 by alkaline hydrolysis afforded 1,3,4,5-tetra-O-benzyl-D-sedoheptulose (20). Because the 7-OH of 20 is more reactive than the 2-OH and can therefore be specifically modified, 20 is a useful intermediate for the preparation of 7-O derivatives of sedoheptulose such as the biochemical reagent sedoheptulose-7-O-phorsphate. Galloylation of 20 with benzyl protected gallic acid followed by debenzylation by catalytic hydrogenation afforded the target product 1. The physico-chemical properties and spectroscopic data of 1 were identical to that of the natural 7-O-galloyl-D-sedoheptulose. The reactions in route 3 are easy to be carried out and an overall yield of over 60% was achieved.   Results of immunological evaluation showed that, when used in vitro, 1 could inhibit spontaneous and Con A and LPS induced proliferation of splenocytes of Balb/c mice; it promoted the spontaneous splenocyte proliferation but suppressed the Con A and LPS induced proliferation of splenocytes after oral administration. These results are similar to that acquired using the natural 7-O-galloyl-D-sedoheptulose.  Following the above mentioned synthetic procedure, some analogues of 1 were synthesized using ferulaic acid, caffeic acid and fructose. The compounds 1, 3, 4, 5-tetra- O- benzyl- 7- O- (4'- O- benzyl- feruloyl)- D- sedoheprulose (25), 1, 3, 4, 5- tetra -O- benzyl- 7- O- (3', 4'- O- benzyl- caffeoyl)- D- sedoheptulose (26), (3', 4', 5'- tri- O-benzyl- galloyl)- 2, 3: 4, 5- di- O- isopropylidene- D- fructopyranose (36) and 1, 2: 4, 5-di- O- isopropylidene- 3- O- (3', 4', 5'- tri- O- benzyl- galloyl)- D- fructopyranose (37) have been prepared. Their immunological activities will be evaluated after deprotection.  In this study, an appropriate method for opening the internal acetal of 2,7-anhydro-D-sedoheptulose was established; some useful intermediates such as compounds 10, 11 and 20, which can be used for regioselectiv modification of sedoheptulose, were obtained; finally, a facile synthetic approach toward 7-0-galloyl-D-sedoheptulose was achieved. Detailed investigation on the pharmacological activity and potential medicinal use of this compound can be now carried out using the synthetic product.