Proline-Catalyzed Direct Asymmetric Aldol Reactions
2000 · paper · Chemistry
Reports that the amino acid proline catalyzes the direct aldol reaction between unmodified acetone and various aldehydes, mimicking enzyme-style enamine catalysis. With 4-nitrobenzaldehyde it gave the product in 68% yield and 76% enantiomeric excess.
0 findings
None that passed a second check.
8 minor (typos and the like; most checked by the judge only)
Wording "Clearly both the pyrrolidine ring and the carboxylate are essential for efficient catalysis to occur", yet Table 1 entry 7 (drawn with sulfur in the ring, a thiazolidine) gives 67% yield and 73% ee against 68% and 76% for proline (entry 4).
- p. 1 Right column, last paragraph, discussion of Table 1
Clearly both the pyrro-
- p. 2 Table 1, entry 7 (S-containing five-membered ring)
67%
- p. 2 Table 1, entry 4 (proline)
68%
Judge's note: Checked Table 1 on the page 2 image: entry 7 has an S atom in the five-membered ring and shows 67% / 73%; entry 4 (proline) shows 68% / 76%. The text then groups entry 7 with "proline derivatives (entries 7-9)", so the authors use "pyrrolidine ring" loosely for the five-membered ring as against the four- and six-membered rings of entries 3 and 5. The statement is stricter than the table supports, but either reading could be intended.
Second check: another model agreed
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Typo Ref. 1(d) reads "Denmark’s chiral Lewis base-catalyzed Mukayama-type aldol reaction"; the name is spelled Mukaiyama.
- p. 1 footnote (1)(d)
Mukayama-type aldol
- p. 1
Denmark’s chiral Lewis base-catalyzed Mukayama-type aldol reaction
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: the chemist the reaction is named after spells his name Teruaki Mukaiyama. The page 1 footnote image (crops C001-a/C002-a) shows "Mukayama-type aldol" in print, so this is not an extraction artefact. It is a cosmetic misspelling.
Second check: another model agreed
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Typo Page 1, right column: "both pipecolic acid (entry 5) and 2-pyrrolidine carboxamide (entry 6) were uneffective"; the standard word is "ineffective".
- p. 1 right column, discussion of Table 1
carboxamide (entry 6) were uneffective
- p. 1
and 2-pyrrolidine carboxamide (entry 6) were uneffective.
- p. 1 column 2, catalyst screening paragraph
were uneffective
- p. 1
both pipecolic acid (entry 5) and 2-pyrrolidine carboxamide (entry 6) were uneffective
Judge's note: The page 1 image (crops C001-a and C002-a) shows "uneffective" in print. The word is nonstandard, but the meaning is clear, so this is cosmetic.
Second check: another model agreed
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Typo Footnote 2(d) has a stray semicolon after the last author: "Morris, A. J.; Tolan, D. R.; Biochemistry 1994, 33, 12291."
- p. 1 footnote (2)(d)
Tolan, D. R.;
- p. 1
Morris, A. J.; Tolan, D. R.; Biochemistry 1994, 33, 12291.
- p. 1 Footnote (4)(e) and (4)(f)
Lerner. R. A.; Barbas
- p. 1 footnote 2(d)
Tolan, D. R.; Biochemistry 1994
Judge's note: The crop shows the semicolon after "Tolan, D. R." directly before the journal name. Every other entry on both pages ends the author list with the final initial's full stop and no separator. Confirmed for the semicolon only; the "Lerner. R. A." and missing-volume points bundled into this cluster are judged under C005 and C004.
Second check: another model agreed
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Typo Footnote 4(d) omits the volume number: "Chem. Eur. J. 1998, 881-885"; footnote 1(b) cites the same journal and year as "Chem. Eur. J. 1998, 4, 1137".
- p. 1 footnote (4)(d)
Chem. Eur. J. 1998, 881-885
Judge's note: The crop shows no italic volume between "1998," and "881". The volume (4) follows from the paper's own ref 1(b) for the same journal and year, so no outside knowledge is needed. Ref 5(a) (Chem. Lett. 1985, 391-394) also has no volume, but that is a different journal and was not raised.
Second check: none (judge only)
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Typo Footnotes 4(e) and 4(f) print a full stop instead of a comma after the surname: "Sinha, S. C.; Lerner. R. A.; Barbas" and "Zhong, G.; Lerner. R. A.; Barbas".
- p. 1 footnote (4)(e)
Sinha, S. C.; Lerner. R. A.; Barbas
- p. 1 footnote (4)(f)
Zhong, G.; Lerner. R. A.; Barbas
- p. 1 footnote 4(e)
Lerner. R. A.; Barbas
Judge's note: The crop shows a full stop after "Lerner" in both 4(e) and 4(f), while 4(a), 4(c), 4(d), 4(g) and 4(h) in the same footnote print "Lerner, R. A." with a comma.
Second check: none (judge only)
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Typo Page 1, right column: "aliphatic aldehydes react with proline to give either the oxazolidinone and/or various other compounds" mixes "either" with "and/or".
- p. 1 Right column, paragraph after eq 1
to give either the oxazolidinone and/
Judge's note: Read on the page 1 image; the construction is printed as quoted. Grammatical slip only; the meaning is clear.
Second check: none (judge only)
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Typo Footnote 15 opens with a sub-label, "(15) (a) Yanagisawa, A.; Matsumoto, Y.; ...", but has no part (b); Table 2 footnote c cites "Lit.:15a".
- p. 2 footnote (15)
(15) (a) Yanagisawa, A.; Matsumoto, Y.
- p. 2 Table 2, footnote c
Lit.:15a +32.4°
Only the authors can say what is right here.
Judge's note: The page 2 crop shows footnote 15 with a single citation labelled (a), followed directly by footnote 16. Table 2 footnote c cites "15a" and the text cites "1d,15,16". Either a 15(b) was dropped or the label is left over; only the authors can say which.
Second check: none (judge only) · checked by hand