Protecting group free

Hoffmann, R.W. (2006) Protecting-Group-Free Synthesis. Synthesis, 3531-3541. 

The nitration step was the ultimate test of our decision to pursue a protecting group-free strategy. We were very pleased to find that the desired nitroarene... 

Fig. 38 Examples of molecules prepared following new concepts in total synthesis (a) intricarene (220) generated by protective group-free synthesis and (b) late-stage site-selective C-H oxidations to generate eudesmane-type terpenes like 222 or (c) to prepare the hydroxylated artemisinin derivative 223...

There have been few reports only of N-acylations with unprotected amino acids (Scheme 7.3). Such reactions will only yield substantial amounts of the desired product if the (unprotected) amino group in the acylating reagent is difficult to acylate. The examples in Scheme 7.3 show that reaction conditions for performing such transformations with success can sometimes be found for large-scale or industrial preparations, in particular, such protective-group-free shortcuts should always be considered. 

Scheme 7.6 Protecting group-free synthesis of muscarine from 1957.

Scheme 7.10 In situ deprotonation of an interfering acidic group allowing an overall protecting group-free synthesis of hapalindole Q.

Scheme 20 Protecting group-free conversion of (—)-hapalindole (95) to (-l-)-ambiguine H (98) by...

The spiraled architecture of welwitindolinone A isonitrile 196 has inspired the development of a variety of strategies for its construction. A beautifully simple protecting group-free synthesis of (-F)-welwitindolinone A has been achieved by Baran and coworkers [115-117]. As depicted in Scheme 48, the key step for installation of the aU-carbon quaternary center at oxindole C3 involved fluoro-hydroxylation of (—)-fischerindole 1 194 via treatment with aqueous Xep2. The desired natural product, 196, was obtained as a single diastereomer in 44% yield. The origin of the asymmetry at oxindole C3 can be traced back to enantiopure carvone oxide. 

Enantbselective, Protecting-Group-Free Total Synthesis of Sarpagine Alkaloids... 

The Neuville and Zhu groups in 2011 reported a protecting group free enantioselective synthesis of both E) and (Z)-alstoscholarines (28 and 29). While the alstoscholarines do not have the C—7 quaternary center embedded within the akuammiline scaffold, these interesting alkaloids are proposed to arise from akuammUine alkaloids and as such contain many shared structural motifs.For this reason, efforts toward their syntheses win be included in this chapter. 

Kim H, Nagald A, Yoshida J (2011) A flow-microreactor approach to protecting-group-free synthesis using organolithium compounds. Nat Commun 2 264... 

Hoffmann RW (2006) Protecting-group-free synthesis. Synthesis 3531—3541... 

The two-step, protective-group-free deoxygenatiOTi of methyl a-o-glucopyranoside is depicted in Scheme 16. 

An organocatalytic desymmetrization of a /neso-anhydride was also the starting point in a recent efficient protecting group-free total synthesis of the monoterpenoid... 

Gerfaud T, Xie CS, Neuville L, Zhu JP (2011) Protecting-Group-Free Total Synthesis of (Eland (Z)-Alstoscholarine. Angew Chem Int Ed 50 3954... 

Tiefenbacher K, Mulzer J (2007) Protecting-Group-Free Formal Synthesis of Platensimycin. Angew Chem Int Ed 46 8074... 

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