BIOCHIMICA ET BIOPHYSICA ACTA 217

T E N T A T I V E RULES FOR T H E NOMENCLATURE OE CAROTENOIDSt

IUPAC Commission on the Nomenclature of Organic Chemistry and [UPAC-IUB Commissio~ oJ~ Biochemical Nomenclature

I NTRODUCTION

Definitive Rules for the Nomenclature of Carotenoids were approved at the IUPAC I4th Conference (London, 1947; Comples Rendus, pp. 142-143 ) and the I6th Conference (New York, 1951 ; Comptes Rendus, p. I IO). Many recent developments in the carotenoid field have resulted in situations that are not covered adequately by the existing rules ; since these rules were adopted, the number of known naturally occurring carotenoids has increased from some 8o to about 3oo. In 1965, the IUPAC Commission on the Nomenclature of Organic Chemistry and the IUPAC IUB Commission on Biochemical Nomenclature approved the formation of a Subcommission to revise the carotenoid rules. The subcommission consisted of Professor W. Klyne (representative of CBN; and Chairman), Professor S. Veibel (representative of CNOC), Professor C. Bodea, Professor T. W. Goodwin, Dr F. Haxo, Dr O. Islet, Dr S. Liaaen-Jensen, Dr W. Powell, Dr W. Quackenbush, Professor N. A. Sorensen, and Professor B. C. L. Weedon.

The subeommission met in Trondheim in 1966 and considered a number of ap- proaches to the naming of carotenoids.

Subsequently the set of proposals selected by the Trondheim subcommission was refined by an ad hoc "working par ty" (S. Liaaen-Jensen, B. C. L. Weedon, W. Klyne, and I,. C. Cross) to give a set of tentative rules for the nomenclature of this group of naturally occurring chemical compounds that is in accord with both the general traditions of biochemical usage and the principles of organic chemical nomenclature.

These rules are now issued jointly by the IUPAC Commission for the Nomen- clature of Organic Chemistry* and the IUPAC-IUB Commission on Biochemical Nomenclature**. Comments are invited; they should be sent to one or other of the commission chairmen or secretaries***.

The formulae have been reproduced from Biochemistry, IO (197 I) 4827 with kind permission of the American Chemical Society.

* Those who have served on the Commission on the Nonaenclature of Organic Chemistry for varying periods during i967 i971 are the following (present members are shown tly an asterisk): 1'. E. Verkade (Chairman to i97i) , N. Lozac'h* (Chairman from i97i), 1,2. Blfiha*, L. C. Cross*, G. M. Dyson, S. P. Klesney*, \¥. IKlyne*, K. L. Loening*, H. S. Nutt ing, J. Rigaudy*, S. Veibel*, Associate members : R. S. Cahn, H. Griinewald*, K. Hi rayama*. Observer: K. A. Jensen.

** Those who have served on the Commission on Biochemical Nomencla ture for varying periods during 1967 1971 are the following (present members are shown by an asterisk): O. Hoffmann- Ostenhof (Chairman), A. E. Braunste in*, XN. E. Cohn*, J. S. Fruton, B. L. Horecker*, P. t¢arlson*, B. Keil*, \V. l£1yne*, C. Lidbecq*, E. C. Slater, B. C. \¥ebb* , -W. J. \¥helan*. Observer: S. Veibel*. *** Chairman CNOC: Professor N. Lozac'h, Ecole nationale sup~rieure de Chimie, 5 avenue d 'Edimbourg , F- I4Caen , France. Secretary: S. P. Klesney, Central Report Index, 566 Building, The Dow Chemical Company, Midland, 3~Iichigan 4864 o, U.S.A. Chairman CBN: Professor (). Hoffman-Ostenhof, Lehrkanzel fflr Biochemie, UniversitS, t \Vien, \Vfihringerstrasse 38, AIo~)o \:ienna, Austria. Secretary: Dr Waldo E. Cohn, Oak Ridge National Laboratory, Post Office Box Y, Oak Ridge, Tennessee 3783 o, U.S.A.

Biochim. Biophys. Acts, 286 (1972) 2i 7 242

218 IUPAC-IUB COMMISStONS

CONTENTS

R u l e

I. Definition of class of compound 2. The stem name 3- Specific names; end-group designations 4- Numbering of carotenoid hydrocarbons 5. Nor carotenoids and seco carotenoids 6. Changes in hydrogenation level 7. Oxygenated derivatives 8. Numbering of oxygenated derivatives 9. relro Nomenclature

IO. Apo nomenclature I i . Higher carotenoids 12. Stereochemistry 13 . Trivial names

Appendix: Naturally occurring carotenoids having trivial names (compiled by Drs O. Straub and H. Gutmann of F. Hoffmann-La Roche & Co. Limited, Basle).

Rult' Carole~mid [ . Class of Compoz,,nd Carotenoids are a class of hydrocarbons (carotenes) and their oxygenated deriva-

tives (xanthophylls) consisting of eight isoprenoid units joined in such a manner that the arrangement of isoprenoid units is reversed at the center of the molecule so that the two central methyl groups are in a 1,6 positional relationship and the remaining nonterminal methyl groups are in a 1,5 positional relationship. All carotenoids may be formally derived from the acyclic C~0H.~,~ structure (I below), having a long central chain of conjugated double bonds, by (i) hydrogenation, (ii) dehydrogenation, (iii) eyclization, or (iv) oxidation, or any combination of these processes.

f H a f H 3 CH3 C H 3 H H H H N Iq N H H N H

/C. C H C~ C C~...C C C. C~ C C C~ C~ C H/C /CH 3 H3C "XC~H'C ~ "C" ~C ~ ~C ~C" ~C" ~'X~" "~C" "~C" ~C" ~C" ~C'H'C ~C

I I I I H H H H H H H H ~ , , H ~ , , H ~ , , H ~ , , ~_, t'l 3 ~.r'l 3 ~r ' l 3 ~-,n 3

( I )

The class also includes certain compounds that arise from certain rearrange- ments or degradations of the carbon skeleton (I) provided that the two cen{ral methyl groups are retained. This excludes retinol (vitamin A) and related C20 compounds.

For convenience carotenoid formulae are often written in a shorthand form as

, t i I I I i '1 I I I

I

(IA) (General f o r m u l a : b roken lines indicate forinal d ivis ion in to i soprenoid units)

Rule Carote;toid ~. The 5"tern ~\ramc All specific names are based on the stem name "carotene", which corresponds

to the structure and numbering shown in II, where the broken lines at the two ter-

Biochim. Diophys. ~qcia, 280 (1972 ) 2[ 7 2~2

NOMENCLATURE OF CAROTENOIDS 219

minations are intended only to represent two "double-bond equivalents". Individual compounds may have C9 acyclic end groups with two double bonds at positions x,2 and 5,6 (e.g., I I I ) or cyclic end groups (such as IV, V, VI, VII , and VIII) .

t 7 t 6 I I ' ' t o ' s ' ~'~ )~ , o - .

4 ~8 (II)

Rule Carotenoid 3. Specific Names; End-Group Designations 3.;. The name of a specific carotenoid hydrocarbon is constructed by adding

two Greek letters as prefixes to the stem name "carotene" (defined in Rule Carotenoid 2), these prefixes being characteristic of the two C9 end groups.

3.~. The prefixes are

Type Prefix Formula Structure

Acyclic ~ C9H15 I I I Cyclohexene fi, e C9H15 IV, V Cyclopentane n C9H17 VI Aryl q~, Z CgHn VII , VI I I

and correspond to the following end-group modifications

18 46 17

2 4 6 3K /~ I__ 8

4

I I I ;4 IV ; 13

16 17

3 1 " ~ 4 8 4

V;E

t6 46

3 4 4

VI;K VII;# V I I 1 ; x

19 2O

~:~ =6 "8 I0 "12 -14

Note : The choice of locants 16 and 17 for the two methyl groups at C-I is con- sidered in connection with stereochemistry in Rule Carotenoid 12.4.

3.3. The Greek-letter prefixes are cited in alphabetical order; the first is separat- ed from the second by a comma, and the second is connected to the stem name by a hyphen.

Note: The Greek-letter alphabetical order is fl (beta), e (epsilon), • (kappa), q~ (phi), Z (ctfi) ~ (psi).

Biochim. Biophys. Acta, 286 (1972) 217-242

220 I U P A C - I U B co.x~5,n s,~iox s

Examples :

E,E-Carotene

E , X - C a r o t e n e

Notes : (i) The Greek- le t te r prefixes are de r ived : /3 and e: from the symmet r i ca l carotenoids with the t r iv ia l names "f i -carotene" and "e-carotene" , ~ from the symmet - rical capsorubin, W from ~:-ionone, ¢ for phenyl and Z, the nex t Greek le t ter af ter ¢. (ii) ~, Y, and (5, from the t r ivial names ~-, y-, and &carotene , are not used.

3.4. When, in a modified or degraded carotenoid, an end group can be der ived from more than one specific end group, the end group chosen as the basis of the name is t ha t occurr ing earl iest in the a lphabe t i ca l order (see Rule Carotenoid 3.3)-

E x a m p l e :

is a der iva t ive of the fi end group, not the e end group.

Rule Carolc~toid 4. Numberi~g of Carole~zoid Itydrocarbons The basic system of number ing is t ha t shown in s t ruc ture If of Rule Carotenoid

2; the end groups are numbered as ind ica ted in Rule Carotenoid 3- If the two end groups are dissimilar , lower (unprimed) numbers are given to tha t end of the molecule which is associa ted with the Greek- le t t e r prefix ci ted first in the nalne. (All unpr imed locants are ci ted before p r imed locants.*)

Examples :

19 20 18" 4' 17 t 6 I I ~ 3 '

" x . / J 19 - , a l , s ,4 ' ta' 1o' ¢ 6'[ . I~'

g , g - C a r o t e n e

* 1UP:\C Nomencla ture of Organic Chemistry (Sections A, B, and C published by Hutterworths , London, 1971) indicates that , in ranking locants for priority, a primed numeral ranks immediately after the same nulneral unprilned. [n general orgallic nomellclature the common practice is there fore to cite locants in the order x,x',(xq n), (x ;- *z)'. The established sequence in the carotanoic field is, however, to cite all unpr imed numerals before any primed numerals, and this practice is followed in these rules.

Biochim. Biophys. Acla, 286 (1972 ) 217 242

NOMENCLATURE OF CAROTENOIDS 2 2 I

9 20 5' A 3 ~ ' 1 8

3 t6' 4

~, X-Carotene

Note: I t is recommended tha t formulae be drawn so tha t unprimed numbers are on the left-hand side.

Rule Carotenoid 5. Nor Carotenoids and Seco Carolenoids (a) Nor Carolenoids. Elimination of a CHa, CH2, or CH group from a carotenoid

is indicated by the prefix "nor" , which in all cases is preceded by the locant of the carbon a tom tha t has been eliminated. The prefix is nondetachable. When alternatives are possible, the locant a t tached to nor is the lowest possible.* The basic number ing of the carotenoid is retained in the nor carotenoid.

Examples"

17 16 / I 1 ~ 4 ' . , . . t

I 16 ~ ~ ~" ~ , ~ ~ ~ ~ 61. ( 3 3

4 18 16

2, 2'-Dinor-/~,fl-carotene

0 4 t

18 5' - ,

4 t8

16, 17, 16', 17'-Tetranor-~,E-carotene

(b) Seco Carotenoids. Fission of tile bond between two adjacent carbon atoms (other than carbon atoms I and 6) of a cyclic end group, with addition of one or more hydrogen atoms at each terminal group thus created, is indicated by tile prefix "seco", the original carotenoid numbering being retained.

Example :

2, 3 - S e c o - ~, E - c a r o t e n e

* The cont ras t with steroid usage ( IUPAC-1UB I967 Revised Rules for Nomencla ture of Steroids, IUPAC Informat ion Bulletin No. 33, Rule 2S-6; also in Biochim. Biophys. dcta, 164 (I968) 453, and elsewhere), where the prefix " n o r " is associated with the highest permissible number , is to be noted.

Biochim. Biophys. Acta, 286 (1972) 217 242

222 IUPAC IUB COMMISSIONS

Rule Carote~zoid 6. Cha~zges in tIydrogenation Level Carotenoid hydrocarbons, including carotenoid acetylenes and allenes, that

differ in hydrogenation level from the corresponding carotenoid hydrocarbon defined by Rule Carotenoid 3, are named from the latter by use of the prefix "hydro" and "dehydro" together with the locants specifying the carbon atoms at which hydrogen atoms have been added or removed.

These prefixes are nondetachable* and immediately precede the Greek-letter prefixes denoting the end groups, and, if both occur in one name, are cited in the order: dehvdro before hydro (multipliers do not affect the order).

Example : tetradehydrodihydro.

Note: Since, to maintain valency requirements, hydrogen atolns are, formally, always added or removed in pairs these prefixes will always be used with an even- number multiplier, e.g. tetrahydro, didehydro.

Examples :

5 ' ~ 3 ~ 'J'~ 7 , .

Lv.;L. ' . . . . i - " T Y ' F 4 16 ~

5, 6, 7, 8, 1' , 2 ' , 3 ' , 4' , 5 ' , 6 ' , 7 ' , 8 ' - D o d e c a h y d r o - f i , X - c a r o t e n e

7, 8 - D i d e h y d r o - ~, g - c a r o t e n e

6, 7 - D i d e h y d r o - E , E - c a r o t e n e

Rule Carotenoid 7. Ox~,genated Derivatives 7.s. Oxygenated (and other) derivatives of carotenoid hydrocarbons are named

* 1UF'AC Nomencla ture of Organic Chemistry, Rule C-I6.I , allows the prefix "hyd r o" to he detachable or non-detachable and the former has become the established usage in general organic chemistry. However, the coIIllllon practice ill carotenoid llames is now to use this prefix as non- detachable, a practice t ha t is followe(t in this set of rules.

Biochim. Biophys. qcta, z86 (I972) -'I7 -'42

NOMENCLATURE OF CAROTENOIDS 223

by use of suffixes and prefixes according to the rules of general organic chemical nomenclature. *

Of the oxygen-containing characteristic groups present, that occurring earliest in the sequence carboxylic acid, ester of carotenoid acid, aldehyde, ketone, alcohol, ester of carotenoid alcohol, is chosen as principal group (following IUPAC Rule C-Io.3) and is cited by, use of a suffix; all other groups are cited as prefixes.

Examples :

HO ~ O

3-Hydroxy-~, E -caroten-3 '-one

16 ~ O

HO_g ~ E 3-Hydrox~-3 ' -oxo-~, ~-earoten-16-oic acid

7.2. A nonbridging ether group is named by use of the appropriate alkoxy or aryloxy prefix (Rule C-2II.2).

OC2Hs 8' 2

I-Etho×y-I, 2, 7', 8'-tetrahydro-~,,~-carotene

7.3. Oxygen bridges are indicated by use of the prefix "epoxy" ; this prefix is preceded by the locants of the two carbon atoms that form tile bridgeheads of the oxygen bridge.

Note: The prefix "epoxy" denotes replacement, by an oxygen bridge, of a hydrogen atom at each of two carbon atoms already otherwise connected to one an- other. An epoxide, notionally formed by adding an oxygen atom to a double bond, is therefore an epoxydihydro derivative of the original compound.

Examples :

H O ~ OH

5, 6 : 5 ', 6 ' - Diepoxy-5, 6, 5', 6 '-tetrahydr o-/3,/3-carotene-3, 3 ' -diol

* [UPAC Rules, Nomenclature of Organic Chemistry, Subsections C-2 to C- 4.

Biochim. Biophys. Acta, 286 (1972) 217- 242

22 4 IUPAC IUB CO51M~SSIONS

5,S : 5",8'-l)icpoxy-5,8,5",8'-tetrahydro-fl,fi-carotene

7.4. Compounds that may be formally derived from a carotenoid hydrocarbon by the addition of the elements of water (H, OH) or of methanol (H, OCHa) to a double bond are named as "hydroxydihydro" or "methoxydihydro" derivatives.

Examples :

HO ~ v ~ ' ' HO

3, 7 ' - D i h y d r o x y - 7 ' , 8 ' - d i h y d r o - ~ ,E - c a r o t e n - 3 ' - o n e

CH30 ~ 0

7, 7 ' - I ) i m e t h o x y - 7 , 8, 7 ' , 8 ' - t e t r a h y d r o - E,E - c a r o t e n e - 3 , 3 ' - d i o n e

Rule Carote,ioid & Numbering of O:D,genated Derivatives &f. if the two C9 end groups of the parent carotenoid hydrocarbon are dissimilar,

their oxygenated derivatives are numbered according to Rule Carotenoid 4, i.e. the end group designated by the Greek letter occurring earlier in the Greek alphabet receives unprimed loeants.

Examples :

H O ~ O

OH p

2, 4- Dihydroxy- ~, g -c a ro ten -3 ' -one

, " ~ ' ~ OCH3

C H 3 0 ~ C H 3 P

2, 2', 3 ' - Tr imethoxy-~ , E - c a r o t e n e

Biochim. Hiophys. Acta, 286 (I972) 2L 7 24"

NOMENCLATURE OF CAROTENOIDS 225

8.2. (a) If the two C9 end groups of the pa ren t caro tenoid hydroca rbon are iden- tical, then the lowest* locant possible is assigned to the pr incipal group, ci ted as suffix.

(b) If more than one of the group chosen to be ci ted as suffix is present , the nmnber ing is de t e rmined by the pr inciple of lowest locants** appl ied to the suffixes.

(c) If no group qualifies to be ci ted as suffix, then the number ing is de t e rmined b y the principle of lowest locants* for all groups ci ted as prefixes.

E x a m p l e s :

ia)

0 ~ O C H 3 2'-Methoxy-e,e-caroten-3-one (not 2-Methoxy-e, v-caroten-3'-one )

(b)

O O C H a

(c)

2'-Methoxy-e, e-carotene-2, 3'-dione [~ot 2-Methoxy-e, e-carotene-3, 2'-dione; see para(b)]

C H 3 0 , O C H 3 0 , 2 t 3 ~ 6 % 2

3, 2'-Dimethoxy-I, 2, 5', 6'-tetrahydro-~, ~0-carotene [not 2, 3'-Dimethoxy-I', 2', 5, 6-tetrahydro-~0, ~-carotene, I, 2, 3, 2', 5', 6' having priority over 2, 5, 6, I', 2", 3'; see para (c)]

Notes : * In ti le caro tenoid series all unpr imed numbers are ci ted before pr imed numbers and ti le former are therefore considered as " lower t h a n " p r imed numbers , e.g., 2,6,6,I ' ,2 ' ,6 ' , elc. ** W h e n series of locants conta in ing the same number of t e rms are compared te rm b y term, t ha t series is " lowes t" t h a t conta ins the lowest number of the occasion of the first difference [ IUPAC Rule C- i3 . i i ( e ) , footnote i .

Rule Carotenoid 9. retro Nomenclature 9..< The prefix "retro" (pr in ted in italics) and a pa i r of loeants are used to in-

d ica te a shift , b y one posi t ion, of all single and double bonds of the con juga ted polyene sys tem de l inea ted b y the pa i r of locants.

9.2. The pa i r of locants precedes the prefix retro. The first locant is t ha t of the carbon a tom tha t has lost a pro ton , the second t h a t of the carbon t ha t has gained one.

Biochim. Biophys. Acta, 286 (1972) 217-242

226 I U P A C - I U B COMMISSIONS

9.3. Tile prefix and its accompanying locants are placed immediately before, and hyphena ted to, the Greek-letter prefixes of the name defined according to Rule Carotenoid 3.

9.4. The prefix and its associated locants are not detachable from the names defined according to Rule Carotenoid 3.

Examples :

HO ~ O P

3-Hydroxy-6', 7-retro-[3, e-caroten-3Conc

6', 7-rctro e, K-Caroten-3-one

8", ~ l-rctro-fi, ~o-Carotcn i i-olle

R u l e Carotenoid zo. A po N o m e n c l a t u r e

I t is often necessary to designate derivatives in which the carbon skeleton has been shortened by the formal removal of fragments from one or both ends of a carot- enoid.

±o.z. The unitalicized prefix "apo" , preceded by a locant, is used to indicate tha t all of the molecule beyond the carbon a tom corresponding to tha t locant has been replaced by hydrogen atoms. A side-chain methyl group is not considered to be "beyond" tile carbon a tom to which it is attached.

±o.2. The prefix and its locant immediately precede the specific name (Rule Carotenoid 3) unless the loeant associated with the prefix "apo" is greater than 5, in which case there is no need to give a Greek-letter end-group designation for tha t end of the molecule.

zo .3 . For purposes of numbering, etc., an end tha t has been shortened by 5 or less skeletal carbon atoms is considered a ~0 (acyclic) end group.

l o . 4. Tile prefix diapo, preceded by two locants, is used to indicate removal of fragments from both ends of the molecule.

i o . 5. If, in a diapo compound, the two ends of the carotenoid skeleton have been shortened unequally, the lower locant associated with the prefix "diapo" is unprimed.

Biochim. Biophys . Acta, 286 (1972) 217-242

NOMENCLATURE OF CAROTENOIDS

Examples :

2' ~ CHO

2,-~Apo-~, ~ -carot en-2'-M

227

Methyl hydrogen 6, 6'-diapocarotene-6, 6'-dioate (trans-Bixin)

Rule Carotenoid I i . Higher Carotenoids The higher carotenoids are a class of hydrocarbons and their oxygenated deriva-

tives consisting of more than eight isoprenoid units joined in a manner similar to that of the C40 carotenoids. They are named as mono- or disubstituted C40 carotenoids. The numbering of the normal carotenoid is retained.

Examples :

2-(3-Methyl-2-butenyl)-C,~-earotene

H O ~ o H 2, 2' - Bis - (3 - methylbut yl)-/3, ~- carotene - 3", 3'" -diol

oY

2, 2' -Bis-( 3-hydroxy- 3-m ethylbutyl)-~, H-carotene

Rule Carotenoid s2. Stereochemistry i2 . r . Absolute Configuration at Chiral Centers. The absolute configuration at

chiral centers is designated by use of the R S convention*, the symbols being placed, with the corresponding locants, before the carotenoid name.

* For a discussion on the R S convent ion and the use of thickened lines, broken lines, wavy lines, and wedges in displayed formulae, see IUPAC Tentat ive Rules for the Nomencla ture of Organic Chemistry, Section E, Fundamen ta l Stereochemistry, IUPAC Informat ion Bulletin No. 35, P. 68; also published in Biochim. Biophys. Acta, 208 (197 o) I, and elsewhere.

Biochim. Biophys. dcta, 286 (1972) 217-242

228 I U P A C - I U B COMMISSIONS

Example:

O H

: 0

OH 3 £', 5 lt, 3 "S, 5'R)-3, 3' 1)ihydroxy-~', ~'-carotene-6, 6'<lione (Capsorubin)

I2.~. A bsohde Configuration of A llenic Compo~nds. The absolute configuration around allene groups will be similarly designated, when known.

J ' O x ~ / O H

CH3.CO0 ~ " (3'>;, 5"R, (/l~)-3'-Acetoxy-5,(>cpoxy-3,5'-dihydroxy-O',7'-didehydro-5,(~,7,,~,5",O'- hexahydro-/;~, /#caroten-8-one (Fucoxanthin)

1~.3. Geomdrical Co~zfigm'ation arouud Double Bonds. The stem name "carotene" implies tra~zs configuration about all double bonds unless the contrary is indicated. l:ollowing the designation of absolute configuration (if any), geometrical configuration is indicated by citing the double bond or bonds with a cis configuration.

Example :

15 15 ~

Natural phytoenc L5-cis 7. S, i[ , I2, 7", 8", IT', ~2'-octahydro- N, ~/.,- carotene

At trisubstituted double bonds, the term cis refers to the relative position of the two substituents forming parts of the main chain of carbon atoms.

Example: natural bixin methyl hydrogen 9'-cis-6,6'-diapoearotene-6,6'-dioate.

In the absence of definite information on geometrical configuration, cis isomers may be distinguished by prefixes such as neo A, neo U, etc. (@ Zechmeister, "Cis-Trans Isomeric Carotenoids, Vitamins A and Arylpolyenes", Springer-\Terlag, Vienna, z962 ).

The stereochemical prefixes E and Z (see footnote to Rule z2.z and J. Am. Chem. Soc. 9 ° (z968) 5o9) may be used, especially when the prefixes cis and trans might lead to ambiguity.

Biochim. Bi@hys . Acta. 286 (i972) 217-z4z

NOMENCLATURE OF CAROTENOIDS 229

;2. 4. Numbering ofgem-Dimethyl Groups at C-±. In an end group of fl or e type , the two me thy l groups a t t a c h e d to C-I are d is t inguished as follows: when the poten- t ia l ch i ra l i ty is as shown in formula A, i.e. with the polyene chain (R) to the r ight of C-I, the me thy l groups below and above the plane of the paper are numbered 16 and 17, respec t ive ly ; if, wi th the polyene chain (R) to the left, the end group is as shown in B ~, then these des ignat ions are una l te red ; if the end group is as shown in B 2, then t hey are reversed.

t8 t7 17 t6

(A) (B ~ ) (B 2 )

In an acyclic end group, the me thy l group tha t is trans to the main skeletal chain is n u m b e r e d 16 and the me thy l group t ha t is cis is numbered 17, as shown in C.

3

~ H3C~I 2/CH2--- / C = C

t6 H 3 C' ~ H

(C)

Rule Carote~oid I3. Trivial Names The preceding rules are designed to define precisely the s t ruc ture of a given

ca ro teno id b y its name. Use of the senl i sys temat ic names der ived from these rules will g rea t ly assist communica t ion between scientis ts and enable work to be more readi ly re t r ieved from the l i tera ture .

The append ix conta ins a list of some t r iva l names cur ren t ly in use for na tu r a l l y occurr ing caro tenoids ; i t also gives their semisys temat ic names and s t ructures . These t r iva l names will be of va lue in na tu r a l -p roduc t and biochemical work, bu t the i r use in sys temat ic organic work should be restr ic ted. If t r iv ia l names are used in a paper , the semisys temat ic name should ahvays be given, in parentheses or in a footnote at the first ment ion.

Whi le the need to coin a new t r iv ia l name mus t occasional ly arise (e.g., because the s t ruc ture of the compound is unknown), the list in the append ix should not be un- necessar i ly enlarged, nor should s imple der iva t ives of known carotenoids be named b y use of the t r iv ia l name or given a new one.

APPENDIX

Some Na tu ra l l y Occurr ing Carotenoids Hav ing Tr ivia l Names. (Tile examples in this append ix are based on an exhaus t ive list of na tu ra l ly occurr ing carotenoids pre- pared by Dr O. S t raub, which forms Chapter X I I of a book "Caro teno ids" , O. Isler, Ed. , Birkh~iuser, Basel and S tu t t ga r t , I971. The two commissions are g rea t ly in- deb t ed to Dr Isler, Dr S t raub , and the i r colleagues of F. Hof fmann-La Roche Co. L td , Basel, for p rov id ing this l ist of compounds . The list includes a few compounds whose na tu r a l occurrence or s t ruc ture is doubt fu l , bu t whose sys temat i c names illus- t r a t e pa r t i cu l a r poin ts of nomencla ture) .

Biochim. Biophys. Acta 286 (1972) 217-242

2a

vo

.-.1

b9

7 t.J

3 ',4

'-D

ideh

ydro

-/3,

~-c

arot

enc

7 ', 8

"D

ihyd

ro-e

, ~0-

caro

tene

Hyd

roca

rbon

s

15-c

is-7,

8,11

,12,

7',8

'-H

exah

ydro

- G

~-c

arot

ene

~~

\-

-~

Tor

ulen

e

c~-Z

eaca

rote

ne

Phy

tofl

uene

H

exah

ydro

lyco

pcnc

b.o

%0

o

7,8,

11,1

2,1

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a

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