CONTENTS xxiii 



N III. Distribution, Properties, and Chemistry of the Provitamins I) and 

 Vitamins D {continued) 



D. Vitamins D 770 



1 . Occurrence of the Vitamins D 773 



2 . Properties of the Vitamins D 778 



( 1 ) Vitamin Dj 778 



(2) Vitamin D3 780 



(3) Vitamin D4 780 



(4) Other Vitamins D 780 



3 . Standards for the Vitamins D 781 



4 . Structures of the Vitamins D 782 



( 1 ) Vitamin D2 783 



a. Pyrocalciferol and Isopyrocalciferol 787 



(2) Vitamin D3 789 



a. Pyrovitamin D3 and Isopyrovitamin D3 790 



(3) Vitamin D4 790 



(4 ) Vitamin D5 790 



(5) General Structural Requirements for the Vitamins D 791 



5. Synthesis of the Vitamins D 791 



IX. Distribution, Properties, and Chemistry of the Vitamin E Group. . . 793 



1 . Introduction 793 



2. Occurrence of the Tocopherols (Vitamins E) 797 



( 1 ) Distribution in Plant Tissues 797 



(2) Distribution in Animal Tissues 799 



3. Structure of the Tocopherols 804 



( 1 ) a-Tocopherol 804 



(2) /3-Tocopherol 807 



(3) 7-Tocopherol 808 



(4) 5-Tocopherol 809 



4 . Synthesis of the Tocopherols 809 



5 . Properties of the Tocopherols 812 



6 . Standards for Vitamin E 819 



7. Chemical Structure in Relationship to Biological Activity of Vita- 



mins E and of Vitamin-E-Like Compounds 820 



( 1 ) Tocopherols 820 



(2) Chromans and Chromene Derivatives 823 



(3) Coumarins 824 



(4) Coumarans and Coumarones 824 



(5) Phenols 825 



(6) Quinones 825 



(7) Hydroquinones 826 



X. Distribution, Properties, and Chemistry of the Vitamin K Group . . . 829 



1 . Introduction 829 



2 . Occurrence of the K Vitamins 831 



3 . Structure of the K Vitamins 832 



(1) Constitution of Vitamin Ki 832 



(2) Constitution of Vitamin K2 836 



(3) Constitution of Menadione 838 



4 . Synthesis of the K Vitamins 838 



( 1 ) Synthesis of Vitamin Kj 838 



