Table 1.
Enantiomer ratios and abundances of sugar acids of carbonaceous meteorites
| Number of carbons/compound | Percent d EE* | Meteorite† | Abundance, pmol/g (meteorite)‡ | Biological occurrence of acid (and parent sugar)§ |
| 3C acid | ||||
| Glyceric | 0 | All | 80 × 103 (M) | d, Common |
| 4C acids | ||||
| Erythro-2,3-DHB | 0 | M39, M47 | 1 × 103 (M39) | Rare |
| Threo-2,3-DHB | 0 | M39, M47 | 365 (M39) | Rare |
| 2,4-DHB | 0 | M39, M47 | 149 (M39) | Rare |
| 2-Methylglyceric | 0 | M39, M47 | 1 × 103 (M39) | Rare |
| Threonic | 43, 55, 33, 47, 34 | G, M39, M52, M38, ALH | 4 × 103 (M), 32(G) | Common |
| Erythronic | 54 | M39 | 4 × 103 (M), 32(G) | d, common |
| HMG | — | G, M39, M53, M57, LAP | 120 (G) | Rare |
| 5C acids | ||||
| Lxyonic | 61, (d) | M39, (M52) | 502 (M39) | Rare |
| Ribonic | 57 | M39 | 589 (M39) | d, common |
| Xylonic | 82, (d) | M39, (M52) | 889 (M39) | d, common |
| Arabinonic | 60, 47 | M39, M52 | 963 (M39) | l, common |
| 6C acids | ||||
| Allonic | (d) | M39 | tr (M39) | Rare |
| Idonic | (d) | GRA06100 | tr (GRA06100) | Rare |
| Gulonic | (d/l) | M39 | tr (M39) | Rare |
| Talonic | (d) | M39 | 29 (M39) | Rare |
| Galactonic | (d) | M39, GRA06100 | 92 (M39) | d, common |
| Gluconic | (d) | M39, GRA06100 | 273 (M39) | d, common |
| Mannonic | (d/l) | M39 | 743 (M39) | d, common |
ALH, ALH 83102; DHB, dihydroxybutyric; Erythro-2,3-DHB, erythro-2,3-dihydroxybutyric acid; G, GRA95229; LAP, LAP 02333; M39, Murchison 39; M52, Murchison 52, etc.; Threo-2,3-DHB, threo-2,3-dihydroxybutyric acid.
HMG is a nonchiral compound. (d) Indicates the finding of only the d enantiomers of these acids (both enantiomers were searched for). (d/l) indicates the compound is present but the d/l ratio could not be determined. The enantiomer ratios of DHB, Erythro-2,3-DHB, Threo-2,3-DHB, and 2-methylglyceric acid were also measured in a second aliquot of M39 (M39-2) with better enantiomer resolution than shown in Fig. 2. The 5C acids, d-xylonic and d-lyxonic, were also seen in a second meteorite, M52. The d enantiomers of (rare) altronic acid and talonic acid may be present in trace amounts in the GRA 06100 meteorite.
Glyceric acid is racemic (or near racemic) in all examined interior meteorite samples; crust samples are discussed in Discerning Extraterrestrial from Biological Compounds. M38 was acid hydrolyzed.
Not measured in all meteorites. Abundances are approximate; listed values include both enantiomers in chiral compounds. Glyceric acid, erythronic acid, and threonic acid abundances are from Murchison (M) in previous work (8); tr Indicates trace amounts but positive identifications.
Both d- and l-threonic acid are less common in biology than d-erythronic acid. Neither d- nor l-idose, the parent sugar of idonic acid, are known to occur in nature (20).