نتایج جستجو برای: mannich base
تعداد نتایج: 258109 فیلتر نتایج به سال:
The sphingoid base backbones of sphingolipids (sphingosines, sphinganines, 4-hydroxysphinganines and others) are highly bioactive species directly and-in most cases-as their metabolites, the N-acyl-sphingoid bases (ceramides) and sphingoid base 1-phosphates. The complexity of these compounds affords many opportunities to prepare synthetic analogs for studies of sphingolipid metabolism and the f...
For the purpose of this review, strong hydrogen bonds have been defined on the basis of experimental data, such as OH stretching wavenumbers, νOH, and OH chemical shifts, δOH (in the latter case, after correction for ring current effects). Limits for O-H···Y systems are taken as 2800 > νOH > 1800 cm-1, and 19 ppm > δOH > 15 ppm. Recent results as well as an account of theoretical advances are p...
The decarboxylative Mannich reaction (DMR) of b-ketoacids with imines has emerged as a very important tool for the synthesis of natural products and biologically active compounds. The elegant work of Robinson on the total synthesis of ( )-tropinone represents the first practical example of utilizing the DMR as a key step in organic synthesis. Herbert and co-workers and Mangla and Bhakuni then d...
A new chemoselective reductive nitro-Mannich cyclization reaction sequence of nitroalkyl-tethered lactams has been developed. Relying on the rapid and chemoselective iridium(I)-catalyzed reduction of lactams to the corresponding enamine, subsequent nitro-Mannich cyclization of tethered nitroalkyl functionality provides direct access to important alkaloid natural-product-like structures in yield...
Organocatalytic Mannich addition of aldehydes to a formaldehyde-derived iminium species catalyzed by proline-derived chiral pyrrolidines provides beta-amino aldehydes with >/=90% ee. Mechanistic analysis of the proline-catalyzed reactions suggests that non-hydrogen-bonded ionic interactions at the Mannich reaction transition state can influence stereochemical outcome. The beta-amino aldehydes f...
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