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The latter reagent in itself is an acetal and therefore the reaction is actually a cross-acetalisation. Kinetic reaction control results from 2-methoxypropene as the reagent. D-ribose in itself is a hemiacetal and in equilibrium with the pyranose 3. In aqueous solution ribose is 75% pyranose and 25% furanose and a different acetal 4 is formed.
These proceeded through 8 different protecting groups (a methyl ester, five acetals, 20 TBDMS esters, nine p‑methoxybenzyl ethers, four benzoates, a methyl hemiacetal, an acetone acetal and an SEM ester). [109] Palytoxin. The introduction or modification of a protecting group occasionally influences the reactivity of the whole molecule.
Whereas a non-participating group, a group usually without a carboxyl group, will often result in an α-glycoside. Below it can be seen that having an acetyl protecting group at position 2 allows for the formation for an acetoxonium ion intermediate that blocks attack to the bottom face of the ring therefore allowing for the formation of the β ...
Used in a more general sense, the term X,Y-acetal also refers to any functional group that consists of a carbon bearing two heteroatoms X and Y. For example, N,O-acetal refers to compounds of type R 1 R 2 C(OR)(NR' 2) (R,R' ≠ H) also known as a hemiaminal ether or Aminal, a.k.a. aminoacetal.
These protecting groups “lock” the sugars into a rigid chair conformation. When the sugar forms the necessary oxocarbenium ion, it flattens at the anomeric position. This change in configuration is a high-energy transformation when cyclic protecting groups are present, and leads to the sugar being “disarmed”. [3] These groups can be ...
Structure of the benzylidene acetal of glucose. In organic chemistry , a benzylidene acetal is the functional group with the structural formula C 6 H 5 CH(OR) 2 (R = alkyl, aryl). Benzylidene acetals are used as protecting groups in glycochemistry.
Cyclic acetals (8 C) Pages in category "Protecting groups" The following 19 pages are in this category, out of 19 total. This list may not reflect recent changes. ...
In organic chemistry, an acetonide is the functional group composed of the cyclic ketal of a diol with acetone. The more systematic name for this structure is an isopropylidene ketal. Acetonide is a common protecting group for 1,2- and 1,3-diols. [1] The protecting group can be removed by hydrolysis of the ketal using dilute aqueous acid.