Application of the silicon-directed annulation reactions to the total synthesis of natural products & studies directed toward the total synthesis of leiodolide A: preparation of the C13-C29 fragment

Brevisamide was isolated from the red tide dinoflagellate Karenia brevis in 2007. Key features of brevisamide include a substituted tetrahydropyran core and conjugated 3,4-dimethylhepta-2,4-dienal side chain. Total synthesis of brevisamide was highlighted by a stereoselective [4+2]-annulation of a (Z)-crotyl silane to furnish the substituted pyran core and Negishi cross-coupling to construct the conjugated dienal side chain. Successful application of the silane-based annulation methodology provided brevisamide in overall 17 steps and 6.4% overall yield from the known (Z)-crotyl silane. Isatisine A was isolated from the leaf and roots of Isatis indigotica in 2007. Total synthesis of isatisine A commenced with the development of a silyl-directed Mukaiyama-type [3+2]-annulation of an ethoxy allylsilane to construct a tetrahydrofuran core. [3+2]-Annulation reaction of an ethoxy allyl silane with 2-bromocinnamylaldehyde afforded the furan core as a single diastereomer. Further substrate-controlled indole addition and intramolecular copper(I)-mediated amidation provided (+)-isatisine A in overall 12 steps. One-pot Diels-Alder/annulation sequence was developed utilizing a silane-substituted 1,3-diene to give a fused-cyclic scaffold. In this reaction sequence, initial Lewis-acid-promoted Diels-Alder reaction between the silyl-substituted diene and a naphthoquinone constructed an intermediate cyclic allylsilane, and subsequent addition of aldehyde and Lewis acid triggered the annulation to construct a complex cyclic compound with high diastereoselectivity. This one-pot three component reaction sequence allowed for a simple access to various fused-polycyclic compounds, which bear a tetrahydropyran core. Leiodolide A was isolated from the deep-water marine sponge Leiodermatium. Leiodolide A was found to be significantly cytotoxic against HCT-116 human colon carcinoma with IC50 values = 1.4 ug/mL (2.5 uM). Since the natural product leiodolide A was found to comprise less than 0.001% of the dry weight of the sponge, establishing an efficient synthetic method to provide a significant amount of the natural product would be valuable to further biological studies. Our effort to synthesized upper fragment of leiodolide A was conducted through a series of cross-coupling reactions involving Stille coupling. Although proper conditions for the oxidation of (Z)-olefin to introduce the contiguous C15-17 triol system in leiodolide A were not achieved, this synthetic pathway would be useful in the total synthesis of leiodolide A

Mobile Edge Computing Based Immersive Virtual Reality Streaming Scheme

Recently, new services using virtual reality (VR)/augmented reality (AR) have appeared and then exploded in entertainment fields like video games and multimedia contents. In order to efficiently provide these services to users, an infrastructure for mobile cloud computing with powerful computing capabilities is widely utilized. However, existing mobile cloud system utilizes a cloud server located at a relatively long distance, so that there are problems that a user is not effectively provided with personalized immersive multimedia service. So, this paper proposes the home VR streaming system that can provide fast content access time and high immersiveness by using mobile edge computing (MEC)