Revised Section F: Natural Products and Related Compounds

Membership of the Working Party (1982-1997): J. R. Bull (Republic of South Africa); H. A. Favre (Canada); M. A. C. Kaplan (Brazil); L. Maat (Netherlands); A. D. McNaught (UK); G. P. Moss (UK); W. H. Powell (USA); R. Schoenfeld (Australia); O. Weissbach (Federal Republic of Germany).

These Rules are as close as possible to the published version [see P.M. Giles, Jr. Pure Appl. Chem., 1999, 71, 587-643. Copyright IUPAC; reproduced with the permission of IUPAC]. If you need to cite these rules please quote this reference as their source. In the World Wide Web version errors which have been detected have been corrected and in 2004 a list of corrections and other changes was published in Pure Appl. Chem., 2004, 76, 1283-1292. These errors and changes are marked by which is a link to details of the change and where it applies. Many of these errors were detected during the translation of it into German by K.-H. Hellwich. Additional corrections since this list was published are marked by .

A PDF copy of the 1999 document is available, click here.

A PDF copy of the 2004 corrections and changes is available, click here.

For a German translation see Angew. Chem., 2005, 117, 7985-8014.

Contents

• Preamble
• Introduction
• Rules
• RF-1. Biologically Based Trivial Names
• RF-2. Semisystematic Nomenclature for Natural Products
• RF-3. Fundamental Parent Structures
  • 3.1 General Guidelines for Chosing a Fundamental Parent Structure
  • 3.2 Structural Features Allowed for Fundamental Parent Structures
  • 3.3 Semisystematic Names
  • 3.4 Indicated Hydrogen
  • 3.5 Numbering of Fundamental Parent Structures
  • 3.6 Identification of Individual Rings
  • 3.7 Stereochemical Configuration of Fundamental Parent Structures
• RF-4. Skeletal Modification of Fundamental Parent Structures
  • 4.1 Removal of Skeletal Atoms without affecting the Number of Rings
  • 4.2 Addition of Skeletal Atoms without affecting the Number of Rings
  • 4.3 Bond Formation
  • 4.4 Bond Cleavage
  • 4.5 Bond Migration
  • 4.6 Removal of a Terminal Ring
  • 4.7 Combinations of Prefixes for Modifying a Fundamental Parent Structure
• RF-5. Replacement of Skeletal Atoms
  • 5.1 Replacement of a Carbon Atom in a Parent Structure
  • 5.2 Replacement of a Heteroatom in a Parent Structure
  • 5.3 Replacement of a Heteroatom in a Parent Structure by Another Heteroatom
  • 5.4 Indicated Hydrogen
• RF-6. Fusion of Additional Rings
  • 6.1 Rings Derived from Functional Groups
  • 6.2 Fundamental Parent Structure Saturation or Unsaturation
• RF-7. Bridged Fundamental Parent Structures
• RF-8. Bond Order Modifications
  • 8.1 Unsaturation
  • 8.2 Saturation of Double Bonds
  • 8.3 Introduction of Unsaturation
  • 8.4 Rearrangement of a Double Bond
• RF-9. Derivatives of Parent Structures
  • 9.1 Prefixes and Suffixes
  • 9.2 Modifications to Principal Characteristic Groups
  • 9.3 Substituent Prefix Names
  • 9.4 Ring Assemblies and Spiro Derivatives
• RF-10. Stereochemical Modifications
  • 10.1 Fundamental and Modified Parent Structures
  • 10.2 Stereochemical Configurations that are Different
  • 10.3 Configurational Inversion at All Asymmetric Centers
  • 10.4 Configurational Inversion at One Asymmetric Center
  • 10.5 Racemates
  • 10.6 Relative Configuration
• References
• Appendix of Natural Product Fundamental Parent Structures (list of names linked to the structure, one per file). See below for tables of structures.
  • Alkaloids - A to K and L to Y
  • Steroids
  • Terpenoids - A to G and H to U
  • Miscellaneous
• Errata and other changes

The nomenclature of natural products has suffered from much confusion, mostly for historical reasons. The isolation of a new substance, in the early days of the science, generally preceded its characterization by a lengthy period. Thus, these compounds were often assigned trivial names that gave no indication of the structure of the molecule and were often found afterwards to be misleading. Even when the original names were later revised (for example: glycerin to glycerol) the new names often expressed the structure imperfectly and were thus unsuitable for the nomenclatural manipulation that is required to name derivatives or stereoisomers. The result was a proliferation of trivial names that taxed the memory of chemists and obscured important structural relationships.

The resultant disorder in the literature led to the creation of committees of specialists with the task of codifying the naming of compounds in various connected areas of natural-product chemistry, such as steroids, lipids, and carbohydrates. As far as their recommendations have been followed, their efforts have been successful in eliminating confusing or duplicate nomenclature.

It is the aim of the IUPAC Commission on Nomenclature of Organic Chemistry to unite as far as possible all the specialist reports into a single set of recommendations that can be applied in most areas of natural-product chemistry. Accordingly, provisional recommendations were prepared and published as Section F of the IUPAC Organic Nomenclature Rules, first in l976 (ref 1), and then in the 1979 edition of the Rules (ref 2).

Introduction

Section F of these IUPAC Organic Nomenclature Rules is intended to help those working with natural products and related compounds to overcome two difficulties that are encountered frequently in their work:

a. A new compound has been isolated from a natural source, but its structure may be imperfectly known. To allow ready reference to such a compound, a trivial name may be coined for it according to the provisions of Rule RF-1, below.

b. A new compound has been isolated and its structure determined; its systematic name can thus be generated. However, this name may be too cumbersome to be continually inserted into the text of a scientific paper. To overcome this difficulty and show the close similarity to related compounds, a semisystematic name can be created in accordance with Rules RF-2 through RF-10.

From the above explanation, three definitions follow:

i. A trivial name is the name given for convenience to a new compound of yet uncertain structure. Such a name carries no (or minimal) structural information and is generally derived from the biological origin of the material. Trivial names should be formed according to the principles of RF-1, which also offers advice on how the change from a trivial to a semisystematic name can be accomplished in such a manner that the literature can still be retrieved without difficulty.

ii. A systematic name is one based on Sections A-E of the IUPAC Organic Nomenclature Rules (ref 2) and on the more recent Guide to IUPAC Organic Nomenclature (ref 3). It will generally comprise stereo descriptors, followed by prefixes, the "parent", and finally a suffix.

iii. A semisystematic name created according to Rules RF-2 through RF-10, provides a simplified alternative to the systematic name. This is normally achieved by the creation of a "semisystematic parent." There are two general types of semisystematic parents used for naming natural products and related compounds:

(a) Parent hydrides, which are structures that do not have terminal heteroatoms or functional groups and therefore consist only of skeletal atoms and hydrogen, for example, in steroid (ref 4), terpene, carotene (ref 5), and alkaloid nomenclature; this type of semisystematic parent can be treated according to the rules in Sections A-D of the IUPAC Organic Nomenclature Rules (ref 2) and the Guide to IUPAC Organic Nomenclature (ref 3), i.e., a suffix and prefixes indicating substituents and modifications to the skeletal structure may be added.

(b) Functional parents, which are structures that have certain terminal heteroatoms or characteristic groups, such as are found in carbohydrates, amino acids, and nucleosides; suffixes are usually not added to this type of semisystematic parent.

Those who wish to name a new compound will obtain the greatest benefit from the present rules if they bear the following in mind:

i. If the structure is unknown, a trivial name may be formed according to Rule RF-1.

ii. If the structure is known and not unduly complex, systematic nomenclature should be used (ref 2, 3).

iii. If the structure is known and complex, there are three possibilities:

(a) A semisystematic parent name describing most of the skeleton of the compound is already in existence in the literature. This should be used and the new name derived from it by the operations of substitutive nomenclature.

(b) The literature does not contain a semisystematic parent name that describes most of the skeleton of the compound, or a structure closely resembling that skeleton. In that case, a new parent name should be created according to Rules RF-2 through RF-7. If necessary, the degree of saturation or unsaturation is indicated according to Rule RF-8; prefixes and suffixes according to Rule RF-9 and stereo descriptors according to Rule RF-10 are added to arrive at the name of the new compound.

(c) The literature contains a semisystematic name describing a structure not identical with, but closely resembling the skeleton in question. In that case, a number of "structure-modifying prefixes" (such as homo, seco) are available under Rule RF-4. Different skeletal atoms, additional rings and bridges can be described according to RF-5 through RF-7. Placed in front of the existing parent name, such prefixes modify the meaning so that it describes the skeletal structure of the new compound. Rules RF-8 through RF-10 are then brought into play to generate the name of the compound itself.

The appendix to this Section lists illustrative semisystematic parent names and the structures they define.

1. International Union of Pure and Applied Chemistry, "Nomenclature of Organic Chemistry: Section F - Natural Products and Related Compounds, Recommendations 1976", IUPAC Information Bulletin Appendices on Tentative Nomenclature, Symbols, Units, and Standards, No. 53, December, 1976. [also in: Eur. J. Biochem. 86, 1-8 (1978)].

2. International Union of Pure and Applied Chemistry, Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H, l979 edition, Pergamon Press, Oxford, 1979.

3. International Union of Pure and Applied Chemistry, A Guide to IUPAC Nomenclature of Organic Compounds, Blackwell Scientific Publications, Oxford, 1993.

4. International Union of Pure and Applied Chemistry Joint Commission on Biochemical Nomenclature, "Nomenclature of Steroids", Pure Appl. Chem. 61, 1783-1822 (1989). [also in: Eur. J. Biochem. 186, 429-458 (1989) and pages xxx-lix in Dictionary of Steroids (Hill, R.A., Kirk, D.N., Makin, H.L.J. & Murphy, G.M., eds) Chapman & Hall, London 1991].

5. International Union of Biochemistry, International Union of Pure and Applied Chemistry, Commission on Biochemical Nomenclature, "Nomenclature of Carotenoids", Pure Appl. Chem., 41, 405-431 (1975).