Several Contain Butyrolactone Natural Molecular Structure On The Enantioselective Total Synthesis Of Research

The natural product Rhizobialideand the proposed structures for Piliferolide A&C have been totally synthesized in an enantioselective manner.The first part of this thesis deals with the synthesis of Rhizobialide A, a natural butanolide produced by Mesorhizobium sp. CCNWGX022 isolated from licorice (Glycyrrhiza uralensis). The whole synthesis consists of 10 steps of reaction, with an overall yield of 39.3% from gultamic acid featuring a ring-opening of an optically-active epoxide with a lithium alkynylide in the presence of BF3-OEt2, a Dess-Martin Oxidation and a Wittig reaction as the key steps.The second part of this thesis describes the enantioselective total synthesis of the structures proposed for Piliferolide A&C, which were isolated from liquid cultures of Ophiostoma piliferum, a fungus associated with aspen. A convergent strategy has been established for synthesis of the two similar natural products. (R)-glyceral acetonide, a chiral building block readily prepared from D-mannitol, was utilized to generate the key intermediate 3-7 via a two-directional Wittig reaction. Then a two-carbon unit was incorporated into the substrate via a ring-opening of an epoxide by the carbanion derived from dimethyl malonate. An acid-mediated ring-closure followed by decarboxylation established the y-lactone unit. The double bond between the C10 and C11 was assembled via a mild and efficient cross-metathesis reaction. Unexpectedly, the 1H and 13C NMR data of the synthetic samples were not in full consisitence with those reported for the natural Piliferolides A and C. However, the disagreement between the NMR data still remained. In summary, the structures proposed in the literature for the natural piliferolides A and C have been synthesized for the first time through an efficient and enantioselective route. The synthetic samples helped to reveal some erroneous in the NMR data given in the literature.