(2aR,2a1S,5aR,9bR)-4-Isopropyl-7,8-dimethoxy-2a1-methyl-2,2a,2a1,3,5a,9b-hexahydrofluoreno[9,1-bc]furan
, Yuri V. Gatilov 1, Konstantin P. Volcho 1,*, Alexander Yu. Sidorenko 2, Vladimir E. Agabekov 2 and Nariman F. Salakhutdinov 1
Round 1
Reviewer 1 Report
This manuscript describes the preparation of an apparently new heterocyclic compound. However, this procedure has been used for the preparation of similar compounds. The introduction, description of the experiment, and characterization of the compounds seem to be OK. The NMR spectra bear no traces of modification.
Please correct the following typo:
line 119: There is "3,4-dyme..." should be "3,4-dime..."
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this manuscript, Li-Zhulanov, Volcho, and co-workers report the synthesis of a new hexahydrofluorenofuran derivative from a typical terpene, 3-carene, with a clay as a catalyst through Prins cyclization and subsequent Friedel-Crafts reactions. Interestingly, this reaction proceeded without the use of any solvents in a moderate yield (49%), and the product was successfully characterized by single-crystal X-ray diffraction analysis that enabled them to determine the absolute configurations of the product. Similar reactions have already been reported by the authors as cited (e.g. ref. 16), but the title compound is certainly a novel compound according to a database. Therefore, in principle, it would be possible to publish this result in this journal, but before doing so, the following revisions and confirmations would be necessary.
1) In the compound name and chemical structural formula of the title compound, one absolute configuration may be missing, since the 7 position in the numbering in Scheme 3 (upper right corner) appears to also be an asymmetric carbon. If necessary, please correct them.
2) What is the red-colored numbers shown in Scheme 3 (upper right corner)? Although the numbering appears to be based on nomenclature, it does not actually correspond to the name of the title compound, leading to confusion.
3) In the reaction scheme at the bottom of Scheme 3, the leftmost compound has one additional proton, but it is not clear where it came from. It should be clearly stated at what stage the catalyst-derived protons enter and where they exit.
4) In the same scheme, one another absolute configuration at the secondary alcoholic carbon is missing.
5) A brief explanation of the role of the catalyst in this reaction would be helpful.
6) The absolute configurations of the product were determined by ScXRD, but that was after recrystallization and does not guarantee the optical purity of the product after the synthesis (before recrystallization). Specific rotation was measured, but this value does not give any information about optical purity unless the value of the optically pure product is known. I think the information about the optical purity after the synthesis is important to discuss the stereoselectivity of this reaction.
7) Section 3.3 (X-ray diffraction analysis) contains a non-English word (between SHELXT and SHELXL). The "P" in P212121 should be italic.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I believe the authors have responded almost completely to all comments. Therefore, I think this manuscript can be accepted in present form.
