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Merck synthesis

Schiff base-Cu(II) complexes, 2, by Aratani and co-workers [3-6] led to high enantioselectivi-ties in selected intermolecular cyclopropanation reactions, one of which was the critical asymmetrization step in the Sumotomo-Merck synthesis of cilastatin (Eq. 5.2). [Pg.192]

If the cyclisation is not worked up, the product is the alkynyl-lithium that can be added directly to 55 to give the alcohol 54. In the Merck synthesis of efavirenz, this step is used to make a single enantiomer of 64 and this chemistry is discussed in Strategy and Control.16... [Pg.120]

The final stages of the Merck synthesis involved differential oxidation of the C(9), the C(10) and the C(22) secondary hydroxyl groups. Initially, the C(9)-/>"methoxybenzyl group was oxidatively cleaved with 2,3-di-chloro-5,6-dicyano-1,4-benzoquinone (DDQ), and the C(10)-triethylsilyl... [Pg.304]

The TES group is the most labile of the common silyl protecting groups, apart from TMS, and can usually be removed in the presence of TBS, triisopropylsilyl (TIPS) and rerf-butyldiphenylsijyl (TBDPS) groups. Selective deprotection of a TES ether using aqueous trifluoroaoetic acid left two TBS ethers and two TIPS ethers intact in the Merck synthesis of the immunosuppressant FK-506 [Scheme 4.19].22 Weaker acids such as H2O-HOAC-THF (3 5 11) at room temperature,33 HF pyridine24 and pyridinium p-toluenesulfonate [Scheme 4.2Q]23 can accomplish similar transformations. [Pg.203]

Strong protic acids cleave phenolic methyl ethers. Thus hydrogen bromide accomplished the same double demethylation as that depicted in Scheme 4.104.189 The final step in a Merck synthesis of the potent dopamine agonist (A,R)-4-pro-pyl-9-hydroxy naphthoxazine (106 2), a phenolic ether deprotection was accomplished on a large scale using methanesulfonic acid in the presence of methionine as the nucleophile [Scheme 4.106]. 190 191... [Pg.239]

The Nazarov cyclization has also been used industrially. In the Merck synthesis of (+)-indacrinone the indanone unit is formed by an aromatic Nazarov cyclization. ... [Pg.780]

A second example of this methodology comes from the Merck synthesis of homo-tyrosine, an intermediate for a potent do >amine agonist (Scheme 27). The Grignard reagent is added to a solution of 2 equiv. of diethyl oxalate at -20 C. [Pg.425]

In a more direct comparison of the phosphine oxide elimination with the sulfone, Schreiber employed a identical system to Danishefsky, but used the phosphine oxide (422). Reaction with isobutyralde-hyde and subsequent elimination resulted in a 1 1 mixture of the ( )- and (Z)-alkenes (421 equation 98). It appears from the more complex example of the Merck synthesis and from this example, that the Julia coupling proceeds with higher ( )-selectivity, in similar yield. [Pg.800]

This topically active carbonic anhydrase inhibitor is a powerful controller of the elevated intraocular pressure associated with glaucoma, and has been prepared by Merck in > 32% yield in a multistep synthesis starting from (R)-3-hydroxybutyrate [49]. Although the key ketone reduction step has been recently improved by researchers at Zeneca by replacing a chemical process with a biological one [50], the Merck synthesis well illustrates the potentialities of the approach to enantiomerically pure drugs based on the use of chiral non-racemic substrates. [Pg.116]

Scheme 2. Modified Merck synthesis of chaetomellic acids. Scheme 2. Modified Merck synthesis of chaetomellic acids.
Insertion into N-H bond. Of major importance is the recently developped intramolecular carbene insertion into N-H bond, which is the key step in the Merck Synthesis of the 1-carbapenam ring system from diazo precursors. Yields are high, and the reaction is always very selective in one isomer. [Pg.217]

SCHEME 2.18. Merck synthesis of endothelin receptor antagonist 114. [Pg.58]

SCHEME 2.19. Merck synthesis of neurokinin-1 (NKi) receptor antagonist 120. [Pg.58]


See other pages where Merck synthesis is mentioned: [Pg.249]    [Pg.295]    [Pg.175]    [Pg.232]    [Pg.219]    [Pg.50]    [Pg.257]    [Pg.68]    [Pg.175]    [Pg.581]    [Pg.581]    [Pg.26]    [Pg.84]    [Pg.422]    [Pg.196]    [Pg.439]    [Pg.160]    [Pg.50]    [Pg.57]   
See also in sourсe #XX -- [ Pg.162 ]




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