Expeditious Asymmetric Synthesis of Polypropionates Relying on Sulfur Dioxide-Induced C–C Bond Forming Reactions

Round 1

Reviewer 1 Report

“Expeditious asymmetric synthesis of polypropio-2 nates relying on sulfur dioxide-induced C-C bond forming reactions”

This review provide a very useful comprehensive overview on the sulfur dioxide-induced C-C bond 3 forming reactions. The review mainly focused on the stereoselective polyketides. Although there are many synthetic methods to prepare 1,3-polyol unit using propionate derivatives, including catalytic enantioselective methods, the present sulfur dioxide method would offer alternative synthetic route. The present manuscript provides readers with valuable references for usage or further studies. Therefore I recommend that this paper is suitable for publication in Catalysts as is.

Author Response

Many thanks to this referee for the positive comments.

Reviewer 2 Report

The present revision shows the asymmetric synthesis of the polypropionate motif employing sulfur-dioxide-based strategies which, among others, have been profusely developed by the main author. The review is well written and illustrative enough concerning the preparation of these interesting structures present in natural products. Therefore, it deserves publication. However, some minor corrections should be made, as follow:

1) Line 65: “alkenes”.

2) There is a lack of greek letters when necessary (perhaps due to conversion from word to pdf) (i.e. lines 73, 156, 400).

3) No reference is cited when describing Scheme 1. In addition, the addition of the reagents is ordered in a weird way in Scheme 1 (3,2,1). Moreover, the meaning of “HA” in Scheme 1 should be explained in the text.

4) Frequently, the authors add a “+” character before a reagent in many schemes. Addition of this “+” in a reagent sequence presented above a reaction arrow results unnecessary and sometimes confusing (i.e.: schemes 1, 5, 7, 8, 9, 10, 11).

5) The “2” in sulfur dioxide should be subscripted (lines 152, 153, 154, 158, 160, 166, 170, 191, 194, 205….). In addition, subscript ”3” in trifluoroacetic acid (line 171). Also, subscript TiCl4 in line 319.

6) In Scheme 11, there is a reaction arrow after compound 68, and immediately a “+” before compound 68. This should be presented in a clearer way.

Author Response

Many corrections requested by referee 2 are due to changes introduced during the conversion of my original manuscript into the text sent to the referees. I have done the modifications (Greek characters, subscripts) they imply on the file provided.

I also have done modifications in the text to improve language and readability. The text has been read by an English speaking person. A modified manuscript will be sent separately.

Referee 2:

1) Line 65 ?

2) Greek letters disappeared during the editing process

3) Reference [16] has been added. The new legend explains now what AH means 

4) I have suppressed all the unnecessary + signs in the drawings and provided new Schemes; they come with the modified manuscript.

5) subscript added when necessary

6) Modified Scheme 11 provided

Many thanks to referee 2 for the careful reading and nice comments.