Carbohydrate-Based Azacrown Ethers in Asymmetric Syntheses
Round 1
Reviewer 1 Report
In general, the review article is interesting and should be published, although I have some comments on the manuscript format. It would be desirable to give more complete information in the reaction schemes: indicate the catalyst number, its amount (mol%) yields and enantiomeric excess, (wherever possible) because the reader first of all receives information from the reaction schemes, and only then reads the text. Most asymmetric fusion reactions indicate only: Catalyst / THF-diethyl ether-Na2CO3 above the arrows, which looks somewhat monotonous.
Thus, the article should be published with minor corrections
Author Response
The manuscript has been significantly modified. The amount of catalyst used is added to the schemes. The yield and the enantiomeric excess for selected reactions can be read in tables.
Reviewer 2 Report
The reviewed paper presents the results of the research of collected papers of authors and it is kind of resume of investigations concerning synthesis and application of azacrowns functionalized with carbohydrates moieties.
The scientific value of this review is good, but authors should correct general layout and updated for more appropriate data.
First, in introduction part it is necessary to add some recent and older references concerning the topic of this paper. Except self-citation (ref. 9), the other example of carbohydrate-azacrowns conjugates (M. Pietraszkiewicz, J. Jurczak, Tetrahedron 1984, 40, 2961-2970.) is not cited. Similarly, more recent paper (M. Pintal, B. Kryczka, A. Marsura, S. Porwanski, Carbohydr. Res. 2014, 386, 18–22.) along with additional one (A. Rathjens, J. Thiem, Carbohydr. Res. 2017, 438, 18-25 and references cited therein) are missing. In my opinion this is important oversight.
Second, I strongly recommend to change the outline of the presented resume, due to the disorder in the general layout. I would be more logical to separate preparation and applications in asymmetric synthesis. The part entitled “Results and discussion” is rather used for original papers not for reviews. I suggest to put e.g. “Preparation and application of carbohydrate-azacrown ethers in asymmetric syntheses” and divide this part to subchapters e.g. 1. Synthesis; 2. Application. In application part for better clarity please separate the Michael addition, which is main asymmetric process from Darzens reaction and epoxidation. That’s why the manuscript must be reconstructed.
Third, very important remarks. There is no examples of synthetic pathway for preparation of carbohydrates-azacrown derivatives. Also the examples of asymmetric reactions are presented in a very poor version; products possess a stereogenic centers which is not shown; the yields, ‘ee’ values should be given in Schemes, appropriate catalyst number must be insert, and other additional data which shows the conditions and result of the process. I can not accept this way of presentation. Those results are summarized in Conclusions (lines 437-438) which is not depicted in Schemes.
Finally, for compound 32 diethyl malonate with R substituent should be numbered as 32a, 32b, etc. Especially, in Scheme 10 R is not specified, even in text (see line 336-337). In addition schemes 7, 8 and 9 shows the same reaction protocol with various Michael acceptors and I recommend to prepare one scheme instead of three.
In addition some details.
Line 8 - What is meaning of this sentence „A number of derivatives of these macrocycles have been synthesized in the research group.”, which group?
Line 19 – “Newer and newer catalysts are …” change into e.g. “The enormous amount of catalysts have been...”
Lines 165-167 – for this problem scheme should be add to show this interesting phenomena
Author Response
The manuscript has been significantly modified according to the evaluation.
In the introduction part, new references are cited:
Tetrahedron 1984, 40, 2976-2970; Carbohydr. Res. 2008, 343, 965-969; Tetrahedron 2009, 65, 6196-6203; Carbohydr. Res. 2014, 386, 18-22; Heteroatom Chem. 2015, 26, 161-167; New J. Chem. 2017, 41, 521-529; C. R. Chim. 2011, 14, 286-300; Carbohydr. Res. 2017, 438, 18-25; J. Carbohydr. Chem. 2016, 35, 397-411.
Syntheses of crown ethers and their application in asymmetric reactions have been separated, section 2 has been divided into subsections. Synthetic pathways for azacrown ethers are also shown in Schemes.
Selected examples of enantioselective syntheses are added, where yields and ee values are given in tables.
In the modified manuscript, the compounds have been renumbered and reordered.
Reviewer 3 Report
In the manuscript, the authors reviewed the development of various chiral crown ethers containing sugar unit in annulation with the macrocyclic ring as the phase transfer catalysts for asymmetric catalysis. This review suggests that monoaza-15-crown-5 lariat ethers incorporating a D-glucose or a D-galactose moiety are the most efficient catalysts. This review is well written, and should be helpful to develop more efficient phase transfer catalyst. I therefore recommend this manuscript for the publication in Chemistry after a minor revision.
- Page 4, in Scheme 2, “…ketones (9) and …(10)” should be “…ketones (12) and …(13)”.
- Where is the Section 3? In page 14, “4. Conclusions” should be “3. Conclusions”.
Author Response
The manuscript has been significantly modified. The compounds have been renumbered and reordered. Section 2 has been divided into subsections. Conclusion is now Section 3.
Round 2
Reviewer 2 Report
Now, in this form can be published.
