I. Studies toward a phosphorus-based chiral auxiliary. II. N-tetrachlorophthaloyl (TCP) for ready protection/deprotection of amino sugar glycosides. III. Total synthesis of NodRf-III (C18:1)(MeFuc).

摘要

(I). Enantiomerically pure phospholanes have shown great promise as reagents for asymmetric synthesis. As such (2;(II). The tetrachlorophthaloyl (TCP) group can be utilized when imidic protection of an amine is desired and durability of the protecting group to conditions ranging from mildly basic to harshly acidic is required. Installation can be accomplished in two steps by treating the free base with the commercially available TCP anhydride and then closing the imidic ring with acetic anhydride and pyridine. Cleavage is effected by 2-4 eq. of ethylenediamine under very mild conditions under which esters and glycopeptides have been shown to be stable. Unsubstituted phthalimides, even within the same molecule, are also unaffected during TCP cleavage. TCP protecting groups serve as ;(III). A convergent stereocontrolled synthesis of the nodulation factor NodRf-III (C18:1, MeFuc) produced by Rhizobium fredii USDA257 has been achieved. Nodulation factors are lipooligosaccharides that are secreted by bacteria which trigger the early steps in the formation of root nodules in leguminous plants. This symbiotic relationship between plant and bacteria plays a major role in the global nitrogen cycle. Key to our synthetic approach was the use of the TCP (TetraChloroPhthaloyl) group to provide for N-differentiation of the linear glucosamine backbone and the use of FeCl