Lethoen or Letheon: How To spell?

The word Lethoen is misspelled against Letheon, a noun meaning "Sulphuric ether used as an anaesthetic agent."

Word contains consecutive vowels 'EO' in between alphabets leth & n is misspelled as 'OE'
Wrong Spelling:  leth-oe-n 
Correct Spelling:  leth-eo-n 
Find more incorrect spellings of Letheon to spell right way.