A t e n step synthesls o f b e n ~o [ a ] p y r e n e -l -~3 C , -2-l3C, o r 3-13C from 2,3,7, llb-tetrahydrobenr[d,e]anthracen-3(1H)-one t s descrlbed t n whtch t h e l n l t l a l step I n v o l v e s t h e condensatlon o f t h l s ketone w l t h t h e l l t h l u m enolate o f e t h y l acetate. bento[a]pyrenes. Key word: benzo[a]pyrene, carbon-13. 13C-NMR, enolates, PAH Thls completes our synthesls o f t h e twelve 13C l a b e l l e d INTROOUCTION Thls l s t h e f l n a l paper I n t h e s e r l e s o f papers descrlbtng t h e syntheses o f a l l twelve o f t h e p o s s l b l e benzo[a]pyrenes l a b e l l e d a t t h e p e r l p h e r a l carbon atoms (1-3). The r e a d l l y accessible 1,2,7,llb-tetrahydrobenz[d,e]anthracen-3(lH)-one (1) was a s u l t a b l e s t a r t l n g m a t e r i a l (4) f o r t h e synthesls o f t h e 1-. 2-. and 3-labelled benzo[a]pyrenes as o u t l i n e d I n Scheme 1. t h e l l t h l u m enolate o f e t h y l a c e t a t e (unlabelled, l a b e l l e d a t C2, o r l a b e l l e d a t C1) i n THF a t -78OC a f f o r d e d t h e expected hydroxy e s t e r 2 l n good y l e l d . Dehydration o f t h e crude hydroxy e s t e r wlth anhydrous formlc a c i d (5) followed by hydrogenatlon over Pd/C gave t h e reduced e s t e r 3 whlch was d l r e c t l y reduced w l t h l l t h l u m alumlnum h y d r l d e t o t h e a l c o h o l 4. Converslon o f t h e alcohol 3 t o t h e c h l o r l d e 5 w l t h t h l o n y l c h l o r l d e followed by treatment w l t h potasslum cyanlde ( l a b e l l e d o r u n l a b e l l e d as needed) i n a c e t o n l t r l l e a f f o r d e d the n l t r l l e 6 whtch was hydrolyzed t o t h e correspondtng a c t d 1 by r e f l u x l n g w l t h a m l x t u r e o f h y d r o c h l o r l c and formtc aclds. anhydrous hydrogen f l u o r l d e gave t h e ketone 8 ( a p p r o p r i a t e l y l a b e l l e d ) , and Condensatlon o f 1 w l t h C y c l l z a t l o n o f the a c l d 1 w l t h *Deceased June 4, 1984.