W. E. Elias University of Victoria Victoria, British Columbia
The Natural Origin of Optically Active Compounds
Pasteur (quoted in l a ) was the first to draw attention to the fact that meso forms of organic molecules occur but rarely in living organisms and, when they do, are most often found to be relatively simple compounds not involved in essential life processes (lb, 2). (Indeed, optical activity is now recognized to be such an inherent feature of life that the failure of other planets to yield optically active material will be taken as evidence for the absence of l i e of complexity comparable with the earth's ($).) Furthermore, with the exception of a mere handful of instances, o d y one optical isomer of a given structure occurs naturally.' This is forcefully illustrated by the example of cholic acid
whose eleven non-identical, tetra-substituted carbon atoms make possible two thousand and forty-eight different configurations, yet only one of these is known to occur naturally. Now, in view of the laboratory experience that only asymmetric compounds can beget asymmetric compo~nds,~ the origin of the present stereoselectiveworld poses an intriguing problem which, since the time of Pasteur's original observation, has served as the spur for research and speculation. It is the purpose of this paper to provide a brief outline of these investigations. Chemical Evolution
Because the problem of the natural origin of optically active molecules is but one facet of the larger problem of the natural origin of organic molecules, a few introductory remarks concerning the concept of chemical evolution are included, hut it is to be noted that what follows is an extremely cursory outline which barely hints a t the extent of the l i t e r a t ~ r e . ~The earliest postulate of the natural origin of organic molecules which is still tenable was conceived independently by Oparin (12) and Haldane (2), who suggested that gases present in the primordial atmosphere could have reacted under natural stimuli such as sunlight or electrical discharges, then products of these reactions could have been carried by rain to the sea where further reactions were possible. These reactions, occurring over periods of time now estimated to he of the order of lo9 yr (IS), could have converted at least 448 / lournol o f Chemical Education
certain areas of the seas into "dilute soups" of organic compounds from which were derived more complex molecules, then protobiological and finally, biological material. In the last twenty years a large amount of experimental evidence has been accumulated to show that mixtures of such gases as were probably present by the time the earth had cooled sufficiently to permit organic compounds to exist, can react to form a wide variety of m o l e ~ u l e s . ~Examples ,~ of these and some possible suhsequent reactions are tabulated in Table 1. Estimates of the seas' maximum total concentration of organic molecules resulting from chemical evolutionary processes vary from 1 to 10% (11, IS), which suggests that the concentration of any particular compound would have been very low and intermolecular reactions unimaginably slow. To overcome this d i i culty, Bernal (19a) has postulated that more concentrated aggregates of molecules could have been formed by adsorption on finely-divided mineral particles along shorelines and in estuaries; at the same time, however, he points out that, in view of the common belief that the elemental compositions of
'Among the few known exceptions to the rule of unique chirality of compounds in nature are the following. Both Dand lraminaacids have been isolated from the proteins of some bacteria (4). Lactic acid formed during muscle contraction is dextrorotatory hut that formed by fermentation of glucose, fructose, and milk is racemic. L-Arabinase is present in gums, pectins, hemicelluloses, and bacterial polysaccharides while the wisomer has been found only in the glycosides of plants of the Aloe group. ¶For s. review of normal laboratory methods for the preparation of optically active compounds, i.e., partial asymmetric syntheses, see references (6, 6 ) . The statement in the text paraphrases that of Japp (7). Selected from among many, references (1, 8-11) together provide a reasonable survey of the concept of chemicd evolution. A good idea of the amount of literature available may be obtained merelv bv scannine the library shelves. Library of Congress classifiEatibn QH 3i5. ~t rs %Gointeresting to note how close some of the ancient writers have come to the concept of such an evolution, as did Lucretius in De Rerum Natura, written about 58 B.C., wherein it is stated that the primordial particles, in infinite time, have moved, and met in all manner of wilvs end tried all combinations, from which arose living creatures! U t the present time of concern for the quality of the environment, it is important to realize that gaseous oxygen probably was not a constituent of the original atmosphere. It is thought that, other than some decomposition of water by natural physical forces, the total amount of free oxygen in the atmosphere is derived from plant metabolic processes. It is estimated that the absence of oxygen and ozone in the primordi$ atmosphere would have allowed ultraviolet radiation 52000 A to reach the earth's surface, thus providing a source of high energy for reactions (11, Chap. 3). J
Toble 1 .
Exompler of Reoctions Carried Out Under "Primitive Conditions"
+ NH, + H20 + H2
CH+ Metal carbides cyano cpds. Amino acids
+
HCHO
+ NHISCN
-
+
+
Reference
+
:$) H>S Dilute solution
or-amino acids RCOzH HCN CO C02 Ns Adenme Adenine Adenine amino acid polymers Rib?se Cyclic polymers Linear polymers} GMW up to 9000, CaCl M g G etc. Acetylene, propylene, etc. Polymers of amino acids
Incubation or uv
Primitive cell-like structures
Spark or silent discharge Electron beam (radioactivity) 30-100°C O T , 4 days UV, or reflux over kaolinite s i v l a t i n g temp. of volcttnic: regions Im act w ~ t hmeteors
today's living organisms reflect the elemental composition of the primordial world, such as the salt in body tissues reflects the salt of the sea, the virtual lack of aluminum and silicon in plant and animal tissues may constitute an important drawback to this mechanism. Alternatively, Bernal has suggested that surfactant organic molecules could have concentrated on the surface of the ocean, been whipped into organically-rich foam by action of wind and wave and, by these agents, been carried to the shore. Both proposals are consistent with the general belief that shallow lagoons heated by the sun and accessible by useful, low-energy radiations are the most likely sites a t which organic molecules could have interacted. Wald (4) has concluded that there are only twentynine "basic elements of biochemistryv-twenty amino acids, five bases (adenine, guanine, cytosine, uracil, thymine), ribose, glucose, fats, and phosphatides. These few molecules permit the formation of proteins, enzymes, DNA and RNA, and provide the sources and storage forms for metabolic energy. Several of these compounds have been prepared in the laboratory under "primitive conditions" (Table 2 ) , providing evidence for the viability of the theory of chemical evolution. It is now thought that, as soon as self-reproducingsystems had been evolved (e.g., SO), chemical evolutionary syntheses progressively decreased in importance and eventually were replaced by biosynthetic syntheses. However, recognition of the relatively small number of essential compounds common t o all living organisms poses the question of how the presumably wide variety of compounds available in the primordial soup could have been refined down to such a relatively small number of product types. Various explanations have been advanced, including "Time's Arrow," which is the picturesque description for thermodynamic and kinetic factors operating in long sequences of reactions over long periods of time (21). For instance, assume that A, X, Y, and Z were early-generation products of chemical evolutionary porcesses, and that A could react with X, with Y and with Z. Then, if the net effect of activation energies and free energy changes favored the reaction A X + K over those of A Y L and A Z M, the competition of X, Y and Z for A would have led to the preferential formation of K. Such factors would have been imposed upon concentration effects and it is conceivable that over long periods of time and through long sequences of reactions the amounts of products of unfavorable sequences gradually decreased to extinction, leaving only the
+
Products
Agents
Reactants
CH,
+
-
Toble 2 .
+ +
+
+ + +
+
(14)
(13) (14 (16, 17) (18) (8) (10~) (9, 19)
(P. 59 for ref) (20)
Ersentiol Compounds which Hove Been Prepared Under Primitive Conditionv
Monomeric unit or-amino a i d s
HCHO Purine and pyrimidine bases monosaccharides HaPo, (available) Carbozylic acids glycerol Pyrrole Aldehvdes
Polymer Polypeptides, proteins, ~. . enzymes Mono- and polysaccharides Nucleic acids, nucleotides, nucleosides Fats Carotenoids, vitamin A, steroids, terpenes, rubber, etc.
a The compounds are italicized when at least one member of the group has been prepared in the lilboratory under primitive conditions. 'The synthesis of this compound has not been proven unequivocaliy. -Obtained a t 1100'K from CI and Ca hydrocarbons (10, p.
104).
nth generation products of the sequences of more favorable reactions. I n addition to these effects it is considered that autocatalysis, where one of the products serves as a catalyst for that reaction, may also have played an important role in determining which products were produced in greater and which in lesser yield (1Ob, I l d , 22). N a t u r a l Production of Optically Active Molecules
With this brief background in hand, the outline of work on the natural origin of optically active molecules may now be considered. Acceptable theories must provide answers to at least five important questions. (1) Were single isomers created by asymmetric syntheses, or did they appear as racemic pairs one isomer of which was preferentially eliminated? (2) If asymmetric synthesis or decomposition is postulated, what was the asymmetric agent? (3) Was the production of an optically-active compound, by whatever means accomplished, an oft-repeated event or one of single occurrence? (4) Are the rotations of compounds the result of chance, i.e., might there be a planet on which Lglucose, n-amino acids, etc., are the naturally occurring compounds? (5) Was asymmetry introduced at an early or late stage of chemical evolution, or was it delayed until the appearance of inchoate life (4, 8, 22) . . . and, how is life to be defined (I If, 19,49)? Absolute Assymetric Syntheses
Belief in the possibility of absolute asymmetric syntheses5has long been held, and postulates of the nature Volume 49, Number 7 , July 1972
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449
Table 3.
Reacttons in which Asymmetry has been Introduced b y Irradiation with Polarized Light
Reaction
ol
of Product
Reference
Humulene nitrosite -r unidentified products Photoresolution of a. r-phenylpyridine derivative Photoresolution of oxalatochramate complexe~ Mutarotation of e- and 8-D-glucopyranose; differentrates in (+)-and (-)-CPL, but same final equilibrium reached
of the asymmetric agent have been as diverse as "shoes and ships and sealing wax, and cabbages and kings." For instance, one may note the existence of theories of unknown directive forces which operated but once (7) and of catastrophic events such as the twist given "earth substances" at the time the moon separated from the earth (93). Pasteur (94) attempted to introduce asymmetry by growing crystals in the field of a powerful magnet, and by carrying out reactions in rapidly rotating tubes, and also attempted to change rotations of naturally-occurring compounds by growing plants under a sun which, by reflection, appeared to rise in the west and set in the east. No optical effects were detected in the products of any of these experiments and, in fact, no progress whatever was made until many years after it bad been postulated that circularly polarized light (CPL) was the only physical agent which possessed the necessary symmetry proper tie^.^ Since then, several asymmetric syntheses under the influence of CPL have been reported (Table 3A) and a like number of asymmetric decompositions of racemic mixtures are also recorded in Table 3B. It is evident that one major objection to the consideration of CPL as the asymmetric agent is the very small rotations which have been produced in the laboratory despite the use of solutions more concentrated and of CPL of greater intensity then predicted to he available naturally (37). However, before dismissing the role of CPL as insignificant, Robinson's work on the optical properties of films should be extended. Robinson (38), studying the tendency of synthetic polypeptides to assume the Grandjean texture of the cholesteric mesophase', was able to show that solutions of several polypeptides had the high rotatory powers characteristic of cholesteric compounds, and recorded rotations between 2 X 104 and 14 X 104 degrees. However, it was not possible to prepare sufficientlyuniform film to demonstrate that light reflected from them was circularly polarized; this is most unfortunate for if it could be shown that a component of (+)- or (-)-CPL was present in the reflected radiation, it vould he possible to speculate that naturalliquid crystals might have been formed in sufficient concentration to produce singlehanded CPL much more intense than predicted to be 450
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Journal o f Chemical Education
available in natural radiation. No work in advance of Robinson's appears to have been undertaken. It is to be expected that quartz and other naturallyoccurring asymmetric crystalss should have been considered as possible initiators of optical activity in organic molecules, although few reactions in which asymmetric catalysts of any type have been used to many instances in the discussion which follows, the stereoisomers mentioned will he enantiomorphs, but in others they may he diastereoisomers or the special diastereoisomers relsted as the n- and 8-anomers of the carbohydrate series, etc. In order to prevent confusion, these terms will be used only when they apply specifically; when a general statement is made, the designation optical isomer will be used. I t is the author's observation that many papers and hooks on the biological aspects of chemical evolution and related topics use the term antipodes rather indiscriminantly. The secondary sources used (65-67) have variously attributed the 1894 hypothesis of the efficacy of circularly polarized light in asymmetric reactions to Curie, to Van't Hoff, and to Le Bel. No attempt has been made to clarify this point by reference to the original literature. 7 Many derivatives of cholesterol form liquid crystals with distinctive physical properties, such compounds being said to exhibit the cholesteric mesophase (Sga, 40). I t is now recognized that tt given mesophase may exist in more than one mesomorphic form and the Grandjean plane tezture is but one of the three polymesomorphio forms which eholesteric compounds can assume. Transition from the readily assumed iocal-conic texture to the Grandjean plane texture is accomplished by the so-called cover slip displacement, i.e., by a simple mechanical motion. I t has been suggested (41) that in the Grandjean plane texture the molecules lie in layers as in smectic liquid crystals, the molecules in each layer being aligned parallel to one another; however, the plane in which the axes lie is different in each layer. The inclinations of the axes vary in a regular manner, increasing in degree through successive layers within each Grandjean plane. The Grandjean plane texture is distinguished by some interesting optical effects, e.g., transmitted and reflected light is polarized, showing extemely high rotations even though the incident light is nan-polarized. When the light is scattered from s. thick sample of compound in the Grandjean plane texture, that in a narrow band of wavelengths is circula~lypolarized. A wide variety of plant and animal tissues and some synthetic esters of triterpenes have been shown to assume the cholesteric mesaphase (Sgb, 46). Both Robinson (58) and Bourdier (quoted in 45, p. 113) have suggested that there may be a relationship between the circularly polarized light reflected from the surface of compounds in the Grandjean plane texture and the origin of optical activity. a For a short list of compounds which are optically sctive only in the crystalline state, see reference (44).
direct the orientation or incoming groups are known (16, 6). Metal-quartz catalysts have been used to bring about the asymmetric hydrogenation of 2,3diphenylpropionic acid, pinene, and a few furan compounds (Ib) a t temperatures above 100°C and pressures above atmospheric, and atkali on quartz was used in the asymmetric cyanoethylation of 2-methyl-cyclohexanone at 2&30°C (lb). Among the asymmetric decompositions reported are the dehydrogenation and oxidation of racemic 2-butanol to yield optically active unreacted alcohol (lb, 45), and racemic menthol and methylethylbutylcarbinol have been partially dehydrated to yield a residue of optically active uureacted alcohol (Ib). Related to these reactions is a report that powdered active quartz readily adsorbed ( 1 - or (-)-ethylenediaminecobalt complexes from their respective racemates (46), but it has also been reported that both (+)- and (-)-quartz have the same effect on L-aminoacids (47). Quite a different approach to the problem has been taken by Akabori (Id) who has designed experiments to test the hypothesis that optical activity would have been introduced into fairly complex molecules. The following scheme has been proposed as a possible natural synthetic route to optically active proteins.
In support of this postulate, Akabori found that dimers and trimers were obtained when aminoacetonitrile was heated with kaolinite at 130°C and that 2-3% of the glycyl residues could be converted to hydroxy-containing residues when polyglycine was spread on clay and treated with formaldehyde or acetaldehyde in the presence of weak bases. Because it was assumed that the polyglycine was adsorbed on the clay so that all molecules would be aligned in a single direction it was thought that the reaction with aldehyde would be stereospecific, but no optical activity has been detected in the products. Moreover, the validity of the first reaction of the sequence has been questioned by Lowe, et al. (48), who pointed out that neither the experimental procedure nor results preclude the possibility that aminoacetonitrile was first converted to amino acids which then polymerized to form polypeptides. More recently Mathews and Moser (16) have shown that aqueous hydrocyanic acid and ammonia react spontaneously at 0°C to form amino acid polymers containing fourteen different residues bonded by what appears to be peptide linkages. Because of the instability of aminoacetonitrile, Mathews
and Moser have suggested that Akabori's results may be explained better by assuming prior hydrolysis of aminoacetonitrile to hydrocyanic acid which then reacted to produce polymers. Natural Resolution of Racemic Mixtures
The foregoing paragraphs contain all of the known experimental evidence to support the postulate of natural asymmetric synthesis so that what follows will provide its own commentary on the relative amount of evidence to support the postulate of natural resolution of racemic mixtures! First, two types of negative results have been interpreted as positive evidence for the prior formation of racemic mixtures. (1) Although many differentcompounds have been synthesized under so-called primitive conditions, as described a t the beginning of this paper, not one has been found to be optically active. However, in the light of Mill's theory (q.v.), these findings might be less significant than appears upon first consideration. (2) It has been found that heating proteic material to temperatures such as used by Fox (8) in his synthesis of polypeptides from amino acids brings about a high degree of racemization. The early idea that spontaneous crystallization could account for the resolution of racemic mixtures has been persistent but far from universally accepted. Many such separations have been reported ((la) and (2.9) for references), but in view of the few known compounds which form separate (+)- and (-)-crystals, the highly specific conditions of temperature and pressure required to separate the enantiomorphs of these favored few and the ease with which spurious results can be obtained in crystallization experiments (.92), caution must be exercised in accepting all of the published claims to success. Other objections to resolution by the crystallization mechanism-that it would have to be a onceonly event and that the D-nessand L-ness of every active compound now known is thus ultimately a matter of c h a n c e a r e not considered insuperable difficulties (q.v.) and, indeed, it has been speculated that organic material on other planets may be enantiomorphic with that found on earth (4, 49). Calvin (fob) accepts the validity of at least two reported spontaneous resolutions (60, 61), but considers them to be examples of stereospecific autocatalysis which can occur only under special conditions: the enantiomorphs must be in rapid equilibrium with one another and crystallization must occur slowly. When these conditions are met the first-formed crystal acts as the stereospecific autocatalyst for separation of more crystals of that enantiomorph, and the (+)-S (-)-equilibrium shifts continuously to compensate for the loss of a single enantiomorph from solution. For example, Allen and Gilard (61) found that racemic mixtures of [Co(en), (H20)(0H-)I2+reacted with dipeptides in which the C-terminal amino acid residue was L- to form mainly the L-cobalt didpeptidecobalt complex; the configuration of the N-terminal amino acid residue appeared to be unimportant. Applying the concept of autocatalysis, the separation of a single enantiomorphic complex would be explained by the following scheme (lob). Volume 49, Number 7, July 1972
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There remains now only the proposal of Mills (59) which is appealing because of its simplicity (Occam's Razor!) hut appears to have been almost completely neglected. Mills points out that, although racemic mixtures are said to contain equal numbers of molecules of the D- and benantiomorphs, this is only a formal definition. Statistically, there is a f i ~ t epossibility that, during a reaction which creates a pair of nonsuperposable mirror images from symmetrical reagents, there will be [(n/2) - x] dextrorotatory and [(n/2) x ] levorotatory molecules formed. Quantitatively, this may be expressed by the equation fraction of enantiomorph in excess = 0.6743/menthol
+ (+)-mandelic acid
XI
[(- >menthy1 (+>mandelatel
8-Radiation from radioactive elements is polarized. When these plane polarized Prays are caused to slow down, circularly polwiriaed Bremsst~ahlungare produced (56-58).
for including the proposal of Mills in this group. Yet, the evidence supporting the other proposals is not strong enough to suggest that these listed in the preceding sentence be considered untenable, and so there is hesitation about condemning any of the theories out of hand. Table 4 shows the theories to be divisible into two groups according to the requirement of a single initiaTable 4. 'Outline of a Critical Summary of the Vatious Theories The lock-and-key concept of reodions between complex molecules.
Theory/Restriction
A
B
C
D
E
F
G
H
Bremsstrahlung
CPL
Asvm. svnthesis
and (-)-menthol
+ (-
kmandelic acid [(
161 was greater
*r
- )-menthy1 (-
kmandelatel
than kt. A recent example is the alreadyquoted reaction of cobalt complexes with dipeptides (51). The diastercomeric products of any similar reaction will have more pronounced steric requirements than the original compounds and when molecules of reasonable complexit,y arc involved, they may be considered to he thrcc-dimmsional bodies of unique shape with rcactivc functional groups placed at definite positions on the surface. In order to react, two such molecules must approach oncanother so that the active functional groups come togcthcr, i.e., the molecules must fit one another as a lock and a key. Thus, if molecule A with reactivc group x (figure), is to react with molcculc B with reactivc group y, the region of B in which y is situated must he of such size and shape as to fit into the region around x. Where B is complex, its mirror image B' could not hc substituted for B. If only A and B exist, half the correctly-oriented collisions which provide the requisite activation energy will result in a reaction. If A and a 1 : 1 mixture of B and B' are used, only two-ninths of such collisions will result in react,ion. If a 1: 1 mixture of A and A' and a 1: 1 mixture of B and B' is used, only one eighth of such collisions result in the production of the desired product A.B, etc. Thus, if A.B is required for a reaction for which A'.B' cannot be substituted, the system containing only A and B will he much more efficient t,han any other of the mixtures described. Thus, it is not difficult to imagine that, after an infinitely-long series of reactions, "what had begun as a relative advantage must have ended as an absolute requirement" (22), the same argument applying to reactions at both thc chemical evolutionary and biosynthesis stages. This outline of studies on the natural origin of optically active compounds is completed by Table 4 in which the main strengths and weaknesses of the various theories arc summarized. It is obvious that thc experimental results arc fragmentary and far too few, but some assessment must be attempted. It seems fair to say that thc mechanism proposed by Akabori, and those involving the intermediacy of optically active crystals such as quartz or simple spontaneous crystallization from racemic mixtures rest on rather more tenuous grounds than others, and there may be grounds
Asym. synthesis Asym. deeomp. Adsorotian related to deed crystals Akabari Stereospecific autac~trtlysis Soontaneous 'crystallisation Statistical variation Resolution of racemates Asvmmetric svnthesis
-
+
A. The initiatina event can have occurred onlv once, or as one reaction in aTing~eseries. B. The configuration of the first single enantiomorph was a matter of chance. C. Two or fewer separate experiments yielding posit,ive evidence have been reported. D. Interpretation of the result$ is not unequivocal. E. The elements1 composition of living organisms does not reflect that in the region where asymmetric syntheses occurred. F. Not supported by evidence from experiments designed to test the theory of chemical evolution. G. The asymmetric agent has not been shown to exist naturally. H. Positive results have been obtained, but the physical eonditmns were not entirely primitive. (This neglects concentrations, d l of which have been much greater than expected naturally.) a (+)-and (-)-quartz are thought to occur with equal frequency on a world-wide scale, although there are individual I n this connection, i t is deposlts of (+)- or (-)-crystrtls. interesting to note that the degree of asymmetric induction is reported to increase as the reaction rate decreases (63).
tion of asymmetry into organic molecules, which is coupled with the attendant conclusion that the configurations of all molecules rest, ultimately, on chance. If this single-event concept is accepted, it is also necessary to imagine a rather fortuitous coincidence of special conditions, i.e., a protected, shallow lagoon on a southern sea shorc in a geologically-stable ares is required to be irradiated by sunlight. Along the shores and bottom of this lagoon there were deposits of either (+)- or (-)-quartz, or the lagoon had shallow areas where evaporation could produce super-saturated solutions from which crystallization could take place of where we may imagine that a series of reactions between molecules of the same compound took place over a reasonably short interval of time, to provide the all-important first single enantiomorph. In the latter two cases, it would also be fitting to imagine that this Molecular Adam was but one member of a pair of enantiomorphs which underwent rapid interconversion so that stereoepecific autocatalysis could lend its aid Volume 49, Number 7, July 1972
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453
in carrying forward the effects of the original genesis of asymmetry. If the single-event concept is rejected, one must still imagine laeoons in similar reeions of the world. but situated so as to receive dilffuse sunlight with its postulated asymmetric circularly polarized component or situated near deposits of radioactive minerals which emitted polarized prays, or must have had bottoms of finely-divided sand so as to allow adsorption of molecules according to Akabori's mechanism. Summary
Thus, the confluence of necessary factors can certainly be imagined and although a high content of coincidence is required, at the present stage of our knowledge we must suppose that the required conditions not only existed but prevailed for sufficient periods of time. Granting this, however, does not obviate the fact that not one of the five questions posed at the beginning of the section on optical activity can be answered! It is true that asymmetric decomposition of a racemic mixture has been accomplished more often and by more different reagents than has absolute asymmetric synthesis, but the number of experiments is, in itself, not a criterion of the intrinsic value of the evidence. Thus, it can only be concluded that no "explanation" can he either accepted or rejected on the basis of evidence now available. It also appears unlikely that experiments can be designed to provide the desired definitive evidence, for chemical evolution cannot be duplicated. As a result, it has been suggested that probes of other planets may hold the best hope for gaining useful information (@), although even this may be a rather forlorn hope! Ideally, it would be most informative if several planets could be reached, and each found to be a t a different stage of chemical evolution. More realistically, one or two planets may be approached in the foreseeable future and found to support either compounds of identical or opposite configurations with respect to those on earth, or DL-compounds only. From such information, no conclusions could be drawn without ruling out coincidence and the idea of a universal panspermia (49), or investigating the chirality of asymmetric radiations and quartz, or establishing that chemical evolution was in a relatively early stage. Be these projected results as they may, the experimental results now available have served to demonstrate that there are plausible explanations, based on natural processes, by which organic compounds may have been produced and then converted into structures of unique chirality, and this is a significant advance over the many experimental failures recorded in the several decades which followed Pasteur's original observation. Literature Cited (1) FLORIIW, M . (Ed&"), "Aspects of the Origin of Life:' Pergarno" p,,~, O r f o ~ d .1960, (a) TERBNT'EV. A. P., A N D KLABDNOYBKII, E . I.. p. 74s: (b] K.,*suwovs~,,, E. I.. p. 105ff: (c) P*",,o"~K*~*, T. E.. A N D P n u s r ~ s x l r ,A. G., p. 9 8 s : ( d ) A a n ~ o s r ,S., p. 116ff; (4 Fox, S. F., p. 148s; (I) MILL^. S. L.. p. 8 5 s . (2) H M ~ L N EJ., B. S.. Rationalist A n n ~ o l p. , 3 (1929). Reprinted in Ref. (ZO), pp. 242-249. (31 STTEB.L.. NASA Accession No. N66-36472. Report No. NASACR-77938: Chcm. Abst?.. 66, 112. 120h (1967).
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Journal o f Chemical Education
(4) Wabo, G.. Proc. Not. Acad. Sci. ( U . S . A . ) .52. 595 (19641. (5) BOTD. D. R.. AND MCKBRVET.M. A.. QuaI1. Em+. 2 5 95 (1968): MORRIBON. J. D.,A N D M O S A E B ,A. S., "Asymmetric Organic Reactions," PrentioeHali. Inc.. Englewood Ctiffs, 1971. E. E.. AND HARRIB. M . M . , Quavt. Rm.. 1, 209 (1947). (6) TURNER. (7) JAPP.F. R., N o l w e , 58,452 (1898). (8) Fox. S. W.. J. C ~ a a r Enuo.. . 34,472 (1957). ~ H., , Chcm. R N . , 70,95 (1970). (9) L ~ n a oR. (10) CALVIN,M.. "Chemic&L Evolution." Ciarendon Presa. Oxford. 1969; (a) Chapter& (b) pp. 149-152: (cl Chapter 7. (11) KENYOA, D. H.. AND STELXIAN. G., "Bioohemical Prrdestination," MeGraw-Hill Book Co.. New York. 1969; (a1 p. 216: (b) p. 215; ( c ) p. 219: (dl pp. 211-212: (el p. 217; 11)11.37. (12) O~*nrrr.A. I. (a) "Genesis and Evolutionary Development of Life." Aoademic Presa. New York. 1968. (b) "The Origin of Life.." MaoMillan Co., New York, 1938: p. 126ff. ( 0 ) Reprinted in Ref. (19). pp. 199-234. (13) Porrli*rPsnnrA. R. M., L ~ a m o u R. . H.. MaRmen, R.. A m CArnlN, M..Proe.Not.Acod. S d . ( U . S . A . ) . 49,737 (1963). (I41 Mzmmn, S. L., Science, 117, 528 (1953); J. Amer. Chem. So&, 77, 2351 (1955). (15) Ono, J., Biochcm. Biophua. Rss. Commun., 2, 407 (19601: O m , J., AND K r l a s ~ m .A,. Amh. Biochcm. Eiophys.. 94, 217 (1961); 96, 293 (1962). . .. N . , AND M o s e n , R. E., N d w a , 2 1 5 , 1 2 3 0 (1967). (16) M A T ~ E WC , P., AND KUDER, J. E., J. Amcr. Chcm. Soc., 92,2527 (1970). (17) F ~ n m sJ. (18) GABEL.N . W.. AND PONNAYPERVMA. C.. Nature. 216.453 (1967). (19) BEnWAL, J. D., "The Origin of Life," Weindenfeld and Nicolson. London, 1967: (a) p. 57: (b) p. 59: (c) p. 37: ( d ) p. 144: ( a ) p. 68. (20) STEINMAN, G.. AND SMITE.A. E.. J. CBEY.EDUC..45, 555 (1968). (21) B ~ M A.. F.. "Time's Arrow and Evolution." (3rd ed.) Prinaeton Univ. Preas. Princeton. N. J.. 1968. p. 155. (22) W n ~ oG.. . Ann. N . Y . Aeod. Sci.. 69,352 (19571. . I.. B d l . Aced. Sei., 5, 633 (19311: quoted in Ref. (23) V ~ n m o s s n V. (4S), p. 110. L., Re% Sn'., Paria. (Ser. 31. 7, 2 (1884): quoted in Ref. (24) PABTEUR, (60). (251 S ~ ~ v e n s o K. n . L.. m n VERDIECH,J. F., J . Amcr. Chem. Soc.. PO, 2974 (1968). (26) Cnme, P., J. Phys., 3,393 (1894); quoted in Ref. ( C J ) , p. 110. (27) Quoted in Ref. (431, p . 110. (28) KARA~ONIS. G.. A N D DRIKOB. G.. N a t w e . 132, 354 (1933). ' Conol. intern. chim.. 2, 112 (19381: 1291 BETTI.M.. AND LUCCRI.E.. AW X Cham. Abstr ,33.7273 (1939). (30) D*um T. L., A N D H w a m R., J. Amsr. Chem. Soc., 57, 377, 1622 (1935). (31) D ~ v r sT. , L., A N D AOHERIAN,J., J. Am". Chsm. Soo., 67,486 (1945). (32) KCBN.W.. A N D BRAUN, E.. N a t u l l ~ i ~17, ~ . .227 (1929): Chsm. AbsC., 23, 2886 (1929). (33) K o n ~ w.. . A N D KNOPB.E.. N a t w m i a ~ . 18. , 183 (19301: Cham. Abah., 24, 2376 (19301, and 2.Phuaik. Chcm.. Abt. B, 7, 292 (1930): Chem. Abatr.. 24, 2439 (1930). S.,J. Chem. Soc.. 1829 (1930). (34) MITCHBLII. . A,, A N D BROWN. E.. 3. Amcr. Cham. Soc., 77, 450 (1955). (35) B ~ n s o l rJ. . Comnt. rand., 199, 198 (19341. (36) S o n ~ r P.. (37) WABLAND. 0. W.. "Advanced Orgsnio Chemistry'' (3rd ed.), John Wiley B Sons, Inc., NewYork. 1960, p. 330. C., Tetrohed., 13, 219 (1961). (381 ROBINBOW, (391 GUY, G. M . , "Moleoular Structure and Propertie8 of Liquid Cryatala," Academic Preas, New York, 1962, (a) pp. 39-49: (b) p. 14. (40) F ~ n a ~ a o hJ . ,L.. Sci. Amer., August, 1964: p. 76. P., AND MEIER, G., i n "Liquid Crystals. 11." BROWN, (41) KABBOBEX. G. M. (Editor), Gordon and Breaoh, London, 1969, pp. 753-762. (42) KNAPP,F. F.. AND NICAOGAS, H. J.. Proceedings of an ACS Symposium on Ordered Fluida and Liquid Crystals. Plenum Press, New York. 1970; pp. 147-168. . "The Photochemical Origin of Life." Academic Preas, (43) D m v ~ m m n A., NewYork. 1956: pp. 107-116. (44) L O W R ~ T., M.. "Optioal Rotstory Power:' Dover Publishing. Inc., New York, 1964 reprint: pp. 346-9. T . quoted in (118). (45) S ~ X E BH., (461 SOHWAB. G. M., ROBT,F., AND RUDOLPR,L., KoUoid-Z., 68, 157 (1934): ScnwAs. G. M . . AND R n n o s ~ n .L.. Nalumiss.. 20, 363
\.""?,. 1,011,
(47) Tsncnro*. R., Koe*u*sa~. M., AND NaLmanA. A,. J . Chcm. Soc. Jopon. 56, 1339 (1935). Chem. Abstr.. SO, 926 (19361. (48) L o n e . C. U.. R m s . M . W.. nlrn M ~ n n ~ n R.. x . Natma. 199. 219 (1963). . L.. P ~ o o r .Cham. Ore. N e t . Plod.. (49) Homwme, N . H.. A N D M m ~ s n S. 20, 423 (1962). (50) H*nwa&. E.. Biochim. Bioghys. Acto.. 13, 171 (1954). (51) ALLEN,D. E., AND GILURD,R. D., Cham. Comm., 1091 (19671. (52) COLLI*N. J. P., AND KIIUR*, E.. J . Amel. Chem. Soc., 89,6096 (1967). (53) BLOUT,E , R., DOTI. P., *NO YANO.J. T..J . A m w . Cham. Soe.. 79, 749 ,747) ~
(541 DOT%P.. AND LUNDBEB~.. R. D.. J . Amcr. Cham. Soo.. 78, 4810 (1956). , S.,Noturc. 219, 338 (1968). (55) G h n ~ rA. (56) U'nmcn~. T. L. V., Awn Vmren. F.. Tetrohcd.. 18,629 (1962) (57) UT.BRICHT,T. L.V.. Quml. Re".. 13.48 (1959). Y.. . I . Theorct. Biol.. 11, 495 (1966). (58) YAIA~ATA. . H.. Chem.Ind.. 750 11932). 1591 M I L L SW. N& 59.53 (1898). i6oj KIP&, F. 8:. AND POPE; w. F. A_'A., J. Amel. Chem. S O C . 74, , 5828 (61) CRAM,D. I.. A N D ECAAFEE. (1952): CUM, D. J., AND KOPICIT, K. R., J. Arne?. Chcm. Soo., 81, 2748 (1959). E , BcI.. 32, 2130 (18991. (621 Mnnczw~fio,W., AND M C K E N ~ IA., D.. AND GROBH. C. K., J . Oro. Chem., 35,657 (1970). (63) NABIPDBI.
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