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Disconnections simplification

Analysis We have an obvious Diels-Alder disconnection, some C-S bonds, and a 1,6-dicarbonyl relationship. The only one that gives any rapid simplification is the D-A, so we ll start with that ... [Pg.86]

Disconnection of non-building-block rings which are embedded in a skeleton and also centrally located, either by breaking one bond or a pair of bonds. The one-bond disconnections which are of value are (a) bonds between C and N, O or S and (b) bonds leading to a totally symmetrical, locally symmetrical, or linear skeleton. The bond-pair disconnections which are most effective in simplification are those which generate two structures of roughly equal complexity. [Pg.39]

The retrosynthetic simplification of 164 which has just been outlined was initiated by the application of a [3,3] sigmatropic rearrangement transform. Other tactical combinations involve the use of such rearrangement transforms to link a pair of disconnective transforms. [Pg.63]

Erythronolide B, the biosynthetic progenitor of the erythromycin antibiotics, was synthesized for the first time, using as a key step a new method for macrolactone ring closure (double activation) which had been devised specifically for this problem. Retrosynthetic simplification included the clearance of the stereocenters at carbons 10 and 11 and the disconnection of the 9,10-bond, leading to precursors A and B. Cyclic stereocontrol and especially the Baeyer-Villiger and halolactonization transforms played a major role in the retrosynthetic simplification of B which was synthesized starting from 2,4,6-trimethylphenol. [Pg.104]

Diene alcohol (38) is the pheromone of the codling moth, tlie creature responsible for the grubs in apples, and of the various possible disconnections (a) is best as it gives most simplification and a stabilised ylid (39) which will produce the requi red trans double bond. Allylic bromide (40) and aldehyde-ester (41) are available,... [Pg.157]

Two disconnections are possible with (3), but we prefer (a) which put the electron-withdrawing C02Et groups on the dienophile and achieves some simplification, This compound was used by Woodward in his synthesis of marasmic aci d, ... [Pg.180]

No doubt (13) would cyclise to (11), but disconnection (b) offers greater simplification. A mixture of (14) and (15) heated under reflux in ethanol with KOH gave 60% of (11) which was used both to synthesise the natural product torreyol and to confirm its structure. [Pg.208]

As a model for his synthesis of vitamin D, Lythgoe " made triene C 2). Disconnection (Wittig) of the central double bond is likely to give the greatest simplification and an a-methylene ketone (43) is one of the starting materials. [Pg.223]

Example The synthesis of aryl cyclohexanones (71) illustrates some of the problems in this area. Of the two possible 1,3-diCO discoonections (71a and b) we may dismiss (a) as it leads to no simplification of the problem. The ring-chain disconnection (b) suggests the acylation of a symmetrical cyclohexanone and so is very promising. [Pg.231]

For syntheses of carotenoids (4), where R is a large group, disconnection (a) achieves the most simplification. How would you make the phosphonium salt (5) needed for this strategy ... [Pg.273]

Disconnection (a) produces greater simplification and (67) can be made from (63), How ... [Pg.353]

Either strategy from p T 253 will work the Darzens disconnection gives (21a) greater simplification. [Pg.362]

Disconnection of the three-membered ring next to the carbonyl group (35a) to give diazoketone (36) achieves maximum simplification. Acid (37) becomes the key intermediate. [Pg.366]

Disconnection of the substituted carbon atom achieves T.aximum simplification and requires diavcoalkane (11). [Pg.375]

Compound (3) is, appropriately enough, a useful intermediate for the synthesis of tetracycline antibiotics. Disconnection (a) gives considerable simplification. [Pg.434]

Two possible intramolecular disconnections are available for the [2.2.2] bicyclo-octane ring system (path A and path B, Scheme 1.4). The choice between the initial [4+2] disconnections A and B at first appears inconsequential leading to idealized intermediates of comparable complexity (54 and 57). However, when the [4+2] and [3+2] disconnections are considered in sequence, the difference becomes clear. For path A, retrosynthetic [3+2] disconnection of intermediate 54 leads to the conceptual precursor 56, which embodies a considerable simplification. In contrast, path B reveals a retrosynthetic [3+2] disconnection of intermediate 57 to provide the precursor 59, a considerably less simplified medium-ring bridged macrocycle. Thus, unification of the [3+2]/[4+2] dual cycloaddition strategy, using the staging... [Pg.8]


See other pages where Disconnections simplification is mentioned: [Pg.570]    [Pg.574]    [Pg.209]    [Pg.9]    [Pg.9]    [Pg.16]    [Pg.21]    [Pg.22]    [Pg.28]    [Pg.29]    [Pg.30]    [Pg.35]    [Pg.37]    [Pg.42]    [Pg.51]    [Pg.60]    [Pg.64]    [Pg.67]    [Pg.82]    [Pg.85]    [Pg.87]    [Pg.91]    [Pg.14]    [Pg.750]    [Pg.19]    [Pg.19]    [Pg.26]    [Pg.31]    [Pg.31]    [Pg.38]    [Pg.39]    [Pg.40]    [Pg.45]    [Pg.47]   
See also in sourсe #XX -- [ Pg.77 ]




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