Scope
The standard conditions for the Weinreb-Nahm ketone synthesis are known to tolerate a wide variety of functional groups elsewhere in the molecule, including alpha-halogen substitution, N-protected amino acids, α-β unsaturation, silyl ethers, various lactams and lactones, sulfonates, sulfinates, and phosphonate esters. A wide variety of nucleophiles can be used in conjunction with the amide. Lithiates and Grignard reagents are most commonly employed; examples involving aliphatic, vinyl, aryl, and alkynyl carbon nucleophiles have been reported. However, with highly basic or sterically hindered nucleophiles, elimination of the methoxide moiety to release formaldehyde can occur as a significant side reaction.
Nonetheless, the Weinreb-Nahm amide figures prominently into many syntheses, serving as an important coupling partner for various fragments. Shown below are key steps involving Weinreb amides in the synthesis of several natural products, including members of the immunosuppressant family of Macrosphelides, and the antibiotic family of Spirofungins.
Read more about this topic: Weinreb Ketone Synthesis
Famous quotes containing the word scope:
“Happy is that mother whose ability to help her children continues on from babyhood and manhood into maturity. Blessed is the son who need not leave his mother at the threshold of the world’s activities, but may always and everywhere have her blessing and her help. Thrice blessed are the son and the mother between whom there exists an association not only physical and affectional, but spiritual and intellectual, and broad and wise as is the scope of each being.”
—Lydia Hoyt Farmer (1842–1903)
“A country survives its legislation. That truth should not comfort the conservative nor depress the radical. For it means that public policy can enlarge its scope and increase its audacity, can try big experiments without trembling too much over the result. This nation could enter upon the most radical experiments and could afford to fail in them.”
—Walter Lippmann (1889–1974)
“Every person is responsible for all the good within the scope of his abilities, and for no more, and none can tell whose sphere is the largest.”
—Gail Hamilton (1833–1896)